briefing document for fda advisory committee meeting for photodynamic therapy with methyl aminolevulinate cream

for treatment of basal cell carcinoma

NDA 21-576

 

 

Sponsor:

PhotoCure ASA

Hoffsveien 48

N-0377 Oslo

Norway

 

 

Sponsor’s Authorized US Agent:

Clementi & Associates

919 Conestoga Road

Rosemont, PA 19010

USA

 

 

Date of Document: 6 August 2003

Date of FDA Advisory Committee Meeting: 10 September 2003

 

 

THE INFORMATION CONTAINED IN THIS DOCUMENT IS CONSIDERED NON-CONFIDENTIAL

 

TABLE OF CONTENTS

1               Introduction........................................................................................... 11

1.1     PhotoCure ASA............................................................................................... 11

1.2     Photodynamic Therapy and Detection for Cancer Diagnosis and Treatment.......................................................................................................................... 11

2               Problem statement............................................................................. 13

2.1     Basal Cell Carcinoma (BCC).......................................................................... 13

2.2     Clinical Factors Relevant to Treatment Options.......................................... 14

2.3     The Need for New Treatments....................................................................... 15

2.4     Photodynamic Therapy with MAL PDT........................................................ 17

3               overview of preclinical development program............. 22

3.1     Pharmacology.................................................................................................. 22

3.2     Acute Toxicity................................................................................................. 22

3.3     Subchronic, Chronic, and Related Toxicity Studies...................................... 23

3.3.1    Hepatotoxicity...................................................................................... 23

3.4     Dermal Application.......................................................................................... 23

3.5     Special Toxicity Studies.................................................................................. 24

3.6     Mutagenicity Studies....................................................................................... 24

3.7     Reproductive Studies...................................................................................... 25

3.8     Carcinogenicity Studies................................................................................... 25

3.9     Absorption, Distribution, Metabolism, Excretion.......................................... 25

3.10   Discussion......................................................................................................... 26

3.11   Conclusions...................................................................................................... 26

4               Overview of clinical development program.................... 39

5               Clinical pharmacology................................................................... 49

5.1     Photoactive Porphyrin Formation.................................................................. 49

5.2     Systemic Absorption........................................................................................ 50

5.3     Selection of Dose Regimen for Pivotal Studies............................................. 51

5.3.1    Concentration and Application Time of MAL Cream....................... 51

5.3.2    Study 101/97......................................................................................... 52

5.3.3    Study 206/98......................................................................................... 55

5.3.4    Study 203/98......................................................................................... 60

5.4     Conclusions on Dosage Selection for Pivotal Studies.................................... 65

5.5     Safety Pharmacology Studies in Healthy Volunteers (Skin Irritation and Sensitization)................................................................................................... 66

5.5.1    Study 107/01......................................................................................... 66

5.5.2    Study 108/01......................................................................................... 66

5.5.3    Study 110/03......................................................................................... 68

5.5.4    Overall Discussion and Conclusions.................................................. 71

6               phase iii program.................................................................................. 72

6.1     Trial Design and Blinding................................................................................ 72

6.1.1    Studies 307/00 and 308/00................................................................... 72

6.1.2    Studies 303/99 and 304/99................................................................... 75

6.1.3    Studies 205/98 and 310/00................................................................... 75

6.2     Trial Populations – Diagnosis and Grading of Lesions.................................. 76

6.2.1    Treatment............................................................................................. 77

6.2.2    Histological Response Assessment..................................................... 79

6.2.3    Primary and Secondary Endpoints..................................................... 79

6.2.4    Safety Parameters................................................................................ 80

6.2.5    Populations for Statistical Analysis.................................................... 80

6.2.6    Statistical Analyses.............................................................................. 81

7               evaluation of efficacy..................................................................... 82

7.1     Overall Patient Population............................................................................. 82

7.2     Efficacy in Low-Risk Primary, Superficial, and Nodular BCC..................... 84

7.2.1    Efficacy in Low-Risk Primary Nodular BCC..................................... 84

7.2.2    Efficacy in Low-Risk Primary Superficial BCC.............................. 101

7.3     Efficacy in High-Risk BCC (Unsuitable for Conventional Therapy)......... 110

7.3.1    Patient and Lesion Disposition......................................................... 110

7.3.2    Patient Demography and Baseline Characteristics......................... 110

7.3.3    Patient Response Rate....................................................................... 113

7.3.4    Lesion Response Rate........................................................................ 113

7.3.5    Cosmetic Outcome............................................................................. 117

7.3.6    Recurrence Rate................................................................................. 119

7.4     Discussion....................................................................................................... 120

7.4.1    Response Rate and Cosmetic Outcome in Low-Risk Nodular BCC 120

7.4.2    Response Rate and Cosmetic Outcome in Low-Risk Superficial BCC    121

7.4.3    Comparison of Response Rate between Studies in Low-Risk Superficial and Nodular BCC........................................................... 122

7.4.4    Response to Re-treatment.................................................................. 122

7.4.5    Response Rate and Cosmetic Outcome in High-Risk BCC (Unsuitable for Conventional Therapy)................................................................ 123

7.5     Conclusion...................................................................................................... 125

8               evaluation of safety........................................................................ 126

8.1     Safety Assessments....................................................................................... 126

8.1.1    Analysis Populations......................................................................... 126

8.1.2    Coding of Adverse Events.................................................................. 126

8.1.3    Adverse Event Definitions................................................................. 127

8.1.4    Clinical Laboratory Evaluations....................................................... 127

8.2     Overall Safety Results.................................................................................. 128

8.2.1    Patient Demographics and Disposition............................................ 128

8.2.2    Number of Lesions Per Patient......................................................... 129

8.2.3    Exposure............................................................................................. 130

8.2.4    Overview of Adverse Events............................................................... 131

8.3     Placebo-Controlled Studies in Primary Nodular BCC................................ 137

8.3.1    Patient Demographics and Disposition............................................ 137

8.3.2    Number of Lesions per Patient......................................................... 138

8.3.3    Exposure............................................................................................. 139

8.3.4    Overview of Adverse Events............................................................... 140

8.3.5    Summary............................................................................................ 147

8.4     Active-Controlled Studies............................................................................. 147

8.4.1    Comparison to Excision Surgery in Primary Nodular BCC............ 147

8.4.2    Comparison to Cryotherapy in Primary Superficial BCC............... 148

8.5     Studies in High-Risk BCC Unsuitable For Conventional Treatment......... 149

8.6     Clinical Assessment of Liver Function......................................................... 150

8.7     Compassionate Use Program (Study 001/97).............................................. 153

8.7.1    Patient Disposition and Demographics............................................ 153

8.7.2    Extent of Exposure............................................................................ 153

8.7.3    Adverse Events................................................................................... 154

8.7.4    Serious or Other Significant Adverse Events................................... 154

8.8     Postmarketing Data...................................................................................... 155

8.8.1    Introduction....................................................................................... 155

8.8.2    Worldwide Market Authorization Status......................................... 155

8.8.3    Patient Exposure................................................................................ 155

8.8.4    Demographics of ADR Reports......................................................... 155

8.8.5    ADR Reports....................................................................................... 156

8.8.6    Conclusion – Post-marketing............................................................ 158

9               regulatory status............................................................................ 159

10             Benefit and risk – role of MAL pdt treatment.................. 160

11             conclusions............................................................................................ 163

12             references.............................................................................................. 164


Tables in Text

Table 1:           Pharmacology Studies. 28

Table 2:           Acute Toxicity Studies. 29

Table 3:           Design of Studies for Repeated Intravenous Administration (Studies 1555/7 and 1555/8) 30

Table 4:           Dose-Related Changes After 7-Day Repeated Intravenous Administration (Study 1555/7) 30

Table 5:           Dose-Related changes after 14-Day Repeated Intravenous Administration (Study 1555/8) 31

Table 6:           Study of Single Dermal Application with Photoactivation. 32

Table 7:           Study of Repeated Dermal Application with Photoactivation. 32

Table 8:           Study of Repeated Dermal Application with Photoactivation. 33

Table 9:           Special Studies Conducted to Assess Local Irritancy and Immunostimulation Induced by Methyl Aminolevulinate. 34

Table 10:         Mutagenicity Studies. 35

Table 11:         Skin Fluorescence After Systemic Administration. 36

Table 12:         Blood Levels of 5-ALA and PpIX After Single Dermal Application. 36

Table 13:         Blood Levels of 5-ALA and PpIX After Repeated Dermal Application with Integral Photoactivation. 37

Table 14:         Skin Localization After Dermal Application. 37

Table 15:         Absorption, Distribution and Excretion after Dermal Application. 38

Table 16:         In Vitro Skin Penetration. 38

Table 17:         Table of Studies in the ISS. 42

Table 18:         PAP Fluorescence in Treated AK Lesions by Cream Concentration and Time of Measurement (Study 206/98) 56

Table 19:         PAP Fluorescence in Treated BCC Lesions by Cream Concentration and Time of Measurement (Study 206/98) 56

Table 20:         PAP Fluorescence in Normal Skin Around AK Lesions by Cream Concentration and Time of Measurement (Study 206/98) 58

Table 21:         PAP Fluorescence in Skin Around BCC Lesions by Cream Concentration and Time of Measurement (Study 206/98) 58

Table 22:         Number of Lesions per Patient 62

Table 23:         Patient and Lesion Response Rates. 62

Table 24:         Number of PDT Treatments per Lesion. 63

Table 25:         Skin Irritation Index. 66

Table 26:         Dermal Response Score. 67

Table 27:         Contact Sensitization Score Following Application with MAL, MAL Vehicle, ALA, and ALA Vehicle. 69

Table 28:         Clinical Trial Population. 83

Table 29:         Patients Randomized and Treated. 84

Table 30:         Number of Lesions Randomized and Treated. 85

Table 31:         Patient Demography. 86

Table 32:         Location of Lesions. 87

Table 33:         Mean Largest Lesion Diameter (mm) per Patient Before Treatment 88

Table 34:         Lesion Depth (mm) Pre-Treatment 88

Table 35:         Number of PDT Sessions per Patient 89

Table 36:         Mean Excision Surgery Margin. 89

Table 37:         Patient Complete Response Rates. 90

Table 38:         Lesion Complete Response Rates. 91

Table 39:         Lesion Complete Response Rates by Lesion Location. 91

Table 40:         Lesion Complete Response Rates by Lesion Depth at Baseline. 92

Table 41:         Lesion Complete Response Rates by Number of PDT Cycles. 94

Table 42:         Patient Complete Response. 95

Table 43:         Lesion Complete Response Rates. 95

Table 44:         Lesion Complete Response Rates by Lesion Location. 96

Table 45:         Lesion Complete Response Rates by Lesion Size. 96

Table 46:         Lesion Complete Response Rates by Number of Treatment Cycles. 97

Table 47:         Patient Cosmetic Outcome 3 months after last PDT or Surgery. 98

Table 48:         Patient Cosmetic Outcome at 12 and 24 Months. 98

Table 49:         Lesion Recurrence Rates at the 12 and 24 Month Assessment 101

Table 50:         Patients Randomized and Treated. 102

Table 51:         Number of Lesions Randomized and Treated. 102

Table 52:         Patient Demography. 103

Table 53:         Patient Distribution by Number of Lesions per Patient 103

Table 54:         Locations of Lesions. 104

Table 55:         Mean Largest Lesion Diameter per Patient Before Treatment 104

Table 56:         Number of Treatment Sessions per Patient 105

Table 57:         Number of Treatment Sessions per Lesion. 105

Table 58:         Patient Complete Response Rate. 106

Table 59:         Lesion Complete Response Rate. 106

Table 60:         Lesion Complete Response Rates by Lesion Location. 107

Table 61:         Lesion Complete Response Rates by Lesion Size. 107

Table 62:         Lesion Complete Response Rates by Number of Treatment Cycles. 108

Table 63:         Patient Cosmetic Outcome 3 months after last MAL-PDT or Cryotherapy. 108

Table 64:         Patient Cosmetic Outcome at 12 and 24 Months. 109

Table 65:         Lesion Recurrence Rates at 12 and 24 Month Assessment 110

Table 66:         Lesion Types. 111

Table 67:         Locations of Lesions. 111

Table 68:         Largest Lesion Diameter (mm) per Patient Before Treatment 112

Table 69:         Number of PDT Sessions per Patient 112

Table 70:         Patient Complete Response Rate. 113

Table 71:         Lesion Complete Response. 114

Table 72:         Lesion Complete Response by Lesion Type. 114

Table 73:         Lesion Response by High Risk Criterion at Inclusion, Lesion Description and Location (Study 310/00) 115

Table 74:         Lesion Complete Response by Lesion Location. 115

Table 75:         Lesion Complete Response by Lesion Size. 116

Table 76:         Lesion Complete Response by Number of PDT Cycles. 117

Table 77:         Patient Cosmetic Outcome 3 months after last PDT. 118

Table 78:         Patient Cosmetic Outcome at 12 and 24 Months. 119

Table 79:         Lesion Recurrence Rates at the 12 and 24 Month Assessment 120

Table 80:         Patient Disposition and Demographic Characteristics in Studies in BCC and AK.. 129

Table 81:         Number of Lesions per Patient in Studies in BCC and AK.. 130

Table 82:         Number of Treatments per Lesion in Studies in BCC and AK.. 130

Table 83:         Summary of Treatment-Emergent Adverse Events in Studies in BCC and AK.. 131

Table 84:         Overview of Local and Non-Local Adverse Events in Studies in BCC and AK.. 132

Table 85:         Local Adverse Events Related to Treatment Reported by ³1% of Patients in Studies in BCC and AK.. 133

Table 86:         Severity of Local Adverse Events Related to Treatment Reported by ³1% of Patients in Studies in BCC and AK.. 134

Table 87:         Non-Local Adverse Events Reported by ³1% of Patients in Studies in BCC and AK.. 135

Table 88:         Patient Disposition and Demographics in Placebo‑Controlled Studies in Primary Nodular BCC.. 138

Table 89:         Number of Lesions per Patient in Placebo‑Controlled Studies in Primary Nodular BCC.. 138

Table 90:         Number of Treatments per Lesion in Placebo‑Controlled Studies in Primary Nodular BCC.. 139

Table 91:         Summary of Treatment-Emergent Adverse Events in Placebo‑Controlled Studies in Primary Nodular BCC.. 140

Table 92:         Overview of Local and Non-Local Adverse Events in Placebo‑Controlled Studies in Primary Nodular BCC.. 141

Table 93:         Local Adverse Events Related to Treatment Reported by ³1% of All Patients in Placebo-Controlled Studies in Primary Nodular BCC.. 142

Table 94:         Severity of Local Adverse Events Related to Treatment Reported by ³1% of All Patients in Placebo‑Controlled Studies in Primary Nodular BCC.. 143

Table 95:         Non-Local Adverse Events Reported by ³1% of All Patients in Placebo‑Controlled Studies in Primary Nodular BCC.. 144

Table 96:         Severity and Relationship to Treatment of Non-Local Adverse Events Reported by ³1% of All Patients in Placebo‑Controlled Studies in Primary Nodular BCC.. 145

Table 97:         Change from Baseline – Studies 202/98 and 203/98. 151

Table 98:         Change from Baseline in Study 205/98 Patients Who Received 2 PDT Sessions. 151

Table 99:         Liver Function Tests in Study 205/98. 152

Table 100:       Demographics in the Compassionate Use Program.. 153

Table 101:       Local Adverse Events in the Compassionate Use Program.. 154

Table 102:       Regulatory Status of MAL Cream.. 159

 


Figures in Text

 

Figure 1:          Efficacy of MAL-PDT in Extensive and Severe Actinic Keratosis. 12

Figure 2:          Build-Up of Photoactive Porphyrins in Normal Skin Following Application of MAL Cream Versus ALA.. 18

Figure 3:          Systemic Absorption of MAL Versus ALA Cream after Topical Application in Mice. 19

Figure 4:          Tumor Selectivity of MAL Cream.. 20

Figure 5:          MAL-PDT Treatment Stages. 21

Figure 6:          Phase III Clinical Development Program for BCC.. 40

Figure 7:          Clinical Development of MAL-PDT in BCC.. 41

Figure 8:          Biosynthetic Pathway of Heme in the Cell Mitochondria. 49

Figure 9:          Measurement of Penetration Depth of MAL in Nodular BCC.. 52

Figure 10:        Depth of PAP Fluorescence in Relation to MAL Cream Concentration and Application Time. 54

Figure 11:        Fluorescence Intensity in BCC Lesions and Normal Skin. 57

Figure 12:        Fluorescence Ratio of BCC Lesion Versus Normal Skin in Relation to Application time. 59

Figure 13:        Fluorescence in PAP Lesions and Normal Skin (Study 206/98) 60

Figure 14:        Processing of Excised Specimen. 73

Figure 15:        Flow Chart for Studies 307/00 and 308/00. 74

Figure 16:        MAL-PDT. 93

Figure 17:        Placebo-PDT. 93

Figure 18:        Cosmetic Outcome, Study 303/99. 99

Figure 19:        Efficacy of MAL-PDT in Low-Risk Nodular BCC.. 100

Figure 20:        Efficacy of MAL-PDT in High-Risk Nodular BCC.. 124

Figure 21:        Efficacy of MAL-PDT in High-Risk Mixed Type BCC.. 125

Figure 22:        Partial Response in Large High-Risk BCC Lesion Following Treatment with MAL-PDT. 162

 

 

ABBREVIATIONS

AE

adverse event

AK

actinic keratosis

ALA

ALP

ALT

AST

5-aminolevulinic acid

alkaline phosphatase

alanine aminotransferase

aspartate aminotransferase

ATC

Anatomic Therapeutic Chemical (classification of drugs)

BCC

basal cell carcinoma

cm

centimeter

CR

complete response

CRF

case report form

eval

evaluation

FDA

Food and Drug Administration

FU

fluorouracil

g

gram

h

hour

ISS

integrated summary of safety

ITT

IV

intent-to-treat

intravenous

J

Joules

m

MAL

month

methyl aminolevulinate

mg

milligram

mW

milliwatt

NDA

New Drug Application

nm

nanometer

NOS

PAP

not otherwise specified

photoactive porphyrins

PDT

PpIX

photodynamic therapy

Protoporphyrin IX

PR

partial response

PMA

premarket approval

SAE

serious adverse event

SD

standard deviation

UK

United Kingdom

US

United States of America

WHO

World Health Organization

1.1         Introduction

1.1        PhotoCure ASA

PhotoCure ASA (PhotoCure) is a pharmaceutical company founded in 1993 by the research foundation at the Norwegian Radium Hospital (NRH) in Oslo. The NRH is the leading cancer hospital in Norway and among the largest in Europe. Basic and clinical research in photobiology has been one of the major research areas at the hospital for the last 20 years. The company develops and markets pharmaceuticals and medical devices for the diagnosis and treatment of cancer and other diseases, using its proprietary photodynamic therapy (PDT) technologies established at NRH. PhotoCure has an important and long-standing research relationship with the Norwegian Radium Hospital Research Foundation. In addition, PhotoCure has ongoing research collaboration with a number of other academic institutions.

1.2        Photodynamic Therapy and Detection for Cancer Diagnosis and Treatment

Photodynamic action involves the activation of a photosensitizer by light. Subsequent energy and electron transfer from the photosensitizing molecules to oxygen induces the formation of reactive oxygen species, which themselves are responsible for cytotoxic reactions. The principle of photodynamic therapy (PDT) is not new in the sense that the ability of certain dyes to sensitize microorganisms for their destruction by a following exposure to light was first mentioned in 1900. For optimization and standardization of PDT, various photosensitizing substances, especially porphyrins have been studied. In 1924, it was observed that hematoporphyrin caused a bright red fluorescence in tumor tissues when illuminated with UV light. Topically applied substances have received increasing interest because they avoid the generalized photosensitization observed with systemically administered photosensitizers. Lately, increasing interest has developed for using precursors of endogenous photosensitizers. Especially, large amounts of preclinical and clinical work have been published on the use of 5-aminolevulinic acid (5‑ALA or ALA). ALA is the precursor of porphyrins in the metabolic pathway of heme synthesis. Exogenous application of ALA leads to increased intracellular production of photoactive porphyrins (PAP), such as protoporphyrin IX. Illumination by light with proper wavelength leads to photoactivation of PAP and cell death.[1]

Recently, it has been shown that derivatives of ALA have important biological properties that are different from ALA and that provide them with unique possibilities for use in diagnosis and treatment of cancer. PhotoCure has now developed medicinal products based on methyl and hexyl esters of ALA, methyl aminolevulinate (MAL) and hexyl aminolevulinate (HAL) respectively. A cream containing MAL together with a light source has been developed for treatment (MAL-PDT) of actinic keratosis (AK) (Figure 1) and basal cell carcinoma (BCC), and a solution of HAL (Hexvix®) for instillation in the bladder before cystoscopy is in advanced clinical development for improved detection of bladder cancer.


Figure 1:         Efficacy of MAL-PDT in Extensive and Severe Actinic Keratosis

 

 

 

 

 

 

 

 

 

 

 

 

 


Figure 1: Efficacy of MAL-PDT in extensive and severe actinic keratosis (AK) (sun-damaged skin).

 


2         Problem statement

2.1        Basal Cell Carcinoma (BCC)

Non-melanoma skin cancers (NMSCs) constitute more than one‑third of all cancers in the United States. The most frequent type of NMSC is BCC and, in fair‑skinned people, BCC of the skin is the most common malignant tumor of any organ.[2] Estimated age‑adjusted incidence figures per 100,000 of the white population in the United States range from 407 to 485 in men and from 212 to 253 in women.2,[3] The number of cases of BCC diagnosed and treated in the United States was estimated at 1,200,000 in 1995.[4] In Australia, the incidence is as high as 1000 to 2000 per 100,000 population2 and in Western Europe the incidence is approximately 200 per 100,000.[5]

The incidence of BCC and other NMSCs is increasing rapidly, as exemplified in the United Kingdom (UK), where it has increased 238% over 14 years.[6] In white populations in Europe, the United States, Canada, and Australia, the average increase of NMSC was 3% to 8% per year over the past 4 decades. The rising incidence of NMSC is probably due to a combination of increased sun exposure or exposure to ultraviolet light due to ozone depletion, increased outdoor activities, and changes in style of clothing. Over 80% of BCCs occur on areas of the body that are frequently exposed to sunlight, namely the head, particularly forehead, nose, cheek, ear and orbit, the neck, and back of the hands.[7] Sun exposure that occurs prior to an age of 20 years is particularly important, and tumors typically occur between 40 and 60 years after the damage was sustained.4,[8],[9] The increase in life expectancy also undoubtedly has contributed since the incidence rises with age. Thus in 1998, the incidence of BCC in individuals over 75 years old was approximately 5 times higher than that of individuals between 50 and 55 years old.[10] There is an increased risk of NMSC in white populations, especially those with blue eyes, a fair complexion, skin type I and II (sunburn easily, suntan poorly, freckle with sun exposure), and red or blond hair. NMSC is uncommon in black populations, Asians, and Hispanics.9,[11]

The majority of BCCs arise on the head and neck where tissue preserving treatment modalities and cosmesis are important for obtaining a successful treatment results.[12],[13],[14] Based on their morphology and histology, most tumors are categorized as nodular, superficial, or morpheaform. In most studies, 45% to 60% are nodular, frequently with ulceration, 15% to 35% are superficial and the remainder are morpheaform, infiltrating or pigmented.14,[15] Histologically, tumor cells resemble those of the basal layer of the epidermis. Mitotic figures may be frequent, despite a usually slow growth rate attrib­utable to a high rate of apoptosis.

BCCs are rarely metastatic and normally run a slowly progressive course of peripheral extension but they have considerable capacity for causing local destruction. In susceptible individuals, tumors are often multiple and new lesions arise over time.[16] Metatypical and morpheaform BCCs are more likely to demonstrate pronounced invasive growth. These aggressive subtypes are associated with high risk of recurrence and morbidity. On the other hand, both nodular and superficial BCCs often exhibit noninfiltrative or superficial growth patterns. These non-aggressive subtypes are generally associated with lower risk as compared with infiltrative and morpheaform BCCs. However, other tumor characteristics, such as size and location may also render these BCCs difficult to treat successfully.

2.2        Clinical Factors Relevant to Treatment Options

There are numerous clinical factors that determine the options for treatment, including the nature of the tumor (primary or recurrent), tumor type, and its location, size, borders, and growth rate.

Overall, it has long been recognized that certain BCC lesions have a high risk of recurrence after conventional treatment.16,[17],[18],[19] For instance, some anatomic sites are more prone to recurrence or even development of metastatic disease, because complete tumor removal is more difficult to achieve.[20] High-risk BCC lesions may have one or more of the following characteristics:

·     Long duration or neglected;

·     Located in adverse anatomic sites, in particular mid-face or ear;

·     Recurrent or inadequately treated;

·     Large tumors, particularly those greater than 20 mm in diameter;

·     Aggressive histological subtype; and/or

·     History of radiation exposure.

Tumors of the mid-face, including the nose, periocular and perioral areas, ears (the so‑called “H-zone”), scalp, and forehead have the highest risk of recurrence.17 Larger tumors, particularly those which show histological signs of infiltration, sclerosis, and multifocality, which tend to occur in areas of sun-damaged skin, are also likely to recur more frequently as compared with non-infiltrating, unifocal nodular and superficial lesions. A history of recurrence is also a predisposing factor to further recurrence. Lesions occurring in patients with multiple lesions also have an increased tendency to recur.18,19 Based on these characteristics for high-risk BCC, the BCC population can be divided into high-risk and low-risk BCC subpopulations, where low-risk BCC are those superficial and nodular lesions that lack the features of high-risk BCC.20

Unfortunately, there are no standardized methods for reporting cure and recurrence rates of BCC and there is a serious lack of prospective comparative studies.15,20,[21] Many series are small, single-center, retrospective, and subject to selection bias. Estimates of the recurrence rate for primary BCC after treatment vary greatly (1% to 39%).15, [22] Despite these limitations, it is clear that 5-year recurrence rates of high‑risk lesions treated with conventional methods are much higher than those of low-risk lesions.17

The main goals in treatment of BCC lesions are to remove the tumor, conserve as much healthy tissue as possible, preserve tissue function, and avoid disfigurement.20 Several surgical procedures are used in the treatment of BCC lesions. Mohs surgery is a specific surgical treatment procedure that has been implemented in the treatment of a subpopulation of (high-risk) BCC lesions. Certain lesion sites (especially the “H-zone”) and lesions of large size may exhibit high risk for subsequent morbidity in regard to disfigurement and reduced functionality.

2.3        The Need for New Treatments

The goals of treatment of BCC are to prevent further local invasion and destruction by achieving a cure, while maximizing tissue conservation, thereby minimizing disfigurement and avoiding interference with function of critical structures such as the nose, eyelids, mouth, and orbit.20 Guidelines for care are provided by the American Academy of Dermatology[23], the National Cancer Institute[24], and the British Association of Dermatologists.[25] However, a recent review of evidence-based treatment options and outcomes stresses the lack of large prospective studies and the paucity of studies comparing 2 treatment modalities.15,20,21,[26] Current treatments represent a compromise between ensuring a cure and obtaining an acceptable cosmetic result. A variety of surgical and non-surgical therapeutic modalities are available for BCC, but cosmetic results are frequently highly unsatisfactory. Thus, new treatment modalities with comparable efficacy to existing methods, which offer better tissue conservation, and result in low treatment‑related morbidity and good cosmetic outcome, are desired.

The choice of treatment modality, which determines the response rate, incidence of recurrence, and cosmetic outcome, depends on the tumor type, histology, definition of margins, size, and site, whether it is primary or recurrent, and also on the expertise of the physician or surgeon. Patient variables such as age, medical status, psychological factors, and concomitant medications should also be taken into account. Surgical excision with primary closure, local flap, or skin graft if required, is the most frequently performed treatment for nodular lesions. Many favor cryotherapy, in particular for superficial lesions. Curettage with or without cauterization of the margins is also frequently used. Radiotherapy is effective, but generally reserved for elderly patients with large lesions who are unsuitable candidates for major surgery and anesthesia. Local cytotoxic agents such as 5-fluorouracil are also used for treatment of superficial lesions but treatment is highly irritant to the skin and recurrence rates are high. Interferon can be effective but it is inconvenient due to the requirement for multiple injections at multiple visits, as well as a high frequency of local and systemic adverse effects.

Although the results of excision surgery for nodular lesions are believed to be good in terms of cure rate, the cosmetic outcome is frequently far from satisfactory with a surgical scar, often in cosmetically sensitive areas. In addition many patients do not like subjecting themselves even to minor surgery. While the prognosis of superficial lesions is generally good, cosmetic results of cryotherapy or surgery are not less problematic than for nodular BCC. These lesions frequently contain islands of papular growth and are bounded by a slightly raised thread-like margin, which is irregular, and may be deficient making delineation of the edge difficult. A wide area of excision is therefore required to minimize the chance of leaving residual tumor. Mixed nodular/superficial lesions share features of both types and present the same difficulties for treatment.

Choice of treatment for high-risk BCC lesions that are not suitable for conventional therapy depends on the type, size, depth, and location of the lesion, together with the skills of the healthcare personnel and resources available to them. The trade-off between eradication on the one hand and cosmetic outcome with preservation of functionality on the other is even more critical than for low-risk lesions. However, the treatment options available are far fewer than for superficial and nodular low-risk lesions. Cryotherapy and electrodesiccation with curettage are not recommended; they are unsuitable for large tumors and incomplete removal of tumor with recurrence is common.[27] Cosmetic results are also frequently unacceptable for all but the smallest tumors, with scarring that is easily seen on sun-damaged skin.[28]

Recurrence rates after surgery of high-risk lesions vary but are dependent on adequate removal of the tumor, which must be histologically controlled. Visual estimation of a margin of 3 to 5 mm is frequently inaccurate with tumor extending beyond the clinically apparent margins. Difficulties in delineation of the lesion caused by scarring further complicate the treatment of recurrent lesions. To prevent recurrence, sacrifice of normal tissue is often substantial with larger margins of 10 mm or more recommended for some lesions. Primary closure may be possible, but healing by second intention with or without subsequent grafting is sometimes the only management option. Scarring may lead to functional disability. Approximately 8% of surgical scars are complicated by the occurrence of keloid or hypertrophy.[29]

Radiation is a useful treatment modality with good cure rates for high-risk lesions either alone or as an adjunct to surgery. However, it is time-consuming and expensive and can lead to complications such as posttreatment fibrosis, chondritis, tissue necrosis, and wound breakdown. Risk of carcinogenesis and radiation dermatitis makes the therapy unsuitable for younger patients. To obtain the best cosmetic results, fractionation is recommended, but multiple treatment sessions are often very inconvenient for elderly patients.

Mohs micrographic surgery27,[30] is probably the optimum form of treatment for recurrent and other forms of BCC with high risk of recurrence. In this procedure, sections of marked, anatomically orientated segments of tissue from the entire periphery of the excision specimen are examined microscopically, with or without immuno-histochemical staining. This provides maximum assurance of tumor clearance with minimal loss of surrounding normal tissue. However, Mohs surgery is very time-consuming and expensive and requires highly specialized staff. Excision and reconstruction of large BCCs may require the additional services of histopathologists, as well as plastic, oculoplastic, or head and neck surgeons.27 This imposes serious constraints on its general applicability.

Therefore, novel treatment options are required for treatment of both low-risk and high‑risk BCC. They should have the following characteristics:

·     Comparable (or superior) response and recurrence rates to those of the best current treatments;

·     Maximum preservation of healthy tissue with good cosmetic and functional outcome;

·     Low treatment-related morbidity;

·     For high-risk lesions, more readily and widely applicable than Mohs surgery;

·     No significant systemic adverse reactions.

2.4        Photodynamic Therapy with MAL PDT

For PDT to be an effective and well-tolerated treatment for BCC, it should meet the above requirements and have the following additional features:

·     No or minimal toxicity other than that associated with the photodynamic response to illumination;

·     Distribution and pharmacokinetic characteristics that favor selectivity for tumor over normal tissue;

·     Rapid clearance after treatment to avoid generalized photosensitivity;

·     High triplet quantum yield and efficient energy transfer to generate singlet oxygen;

·     Strong absorption of light by the photosensitizer in the red part of the visible spectrum, which tissues naturally transmit most effectively and which is non-mutagenic;

·     A reliable light source designed to avoid heating and tissue damage.

Systemic porphyrin-based PDT has the major disadvantage of causing prolonged photosensitivity. To avoid severe phototoxicity, the patient is required to avoid sunlight for several weeks after treatment. An alternative approach is the use of topical application of precursors of the endogenous photosensitizer, protoporphyrin IX (PpIX), and other photoactive porphyrins (PAPs). In some countries, PDT with the precursor of PpIX, 5‑aminolevulinic acid (5-ALA), has been recognized as an effective and safe treatment of premalignant and malignant skin lesions. However, it has limited ability to penetrate the skin of thicker lesions.34 Furthermore, although it shows some selectivity in terms of localization in lesions rather than surrounding normal skin, it is far less selective than 5‑ALA methyl ester (methyl aminolevulinate; MAL).33

As shown in Figure 2, this improved selectivity for tumor tissue by MAL is especially related to the lower build-up of photoactive porphyrins (PAP) in normal skin by topical application of MAL compared with 5-ALA.


Figure 2:         Build-Up of Photoactive Porphyrins in Normal Skin Following Application of MAL Cream Versus ALA

 

 

 

 

 

 

 

 

 

 


Figure 2: Lower build-up of PAP in normal skin after topical application of MAL. The MAL cream and ALA cream were applied topically on 2 adjacent normal skin areas (MAL cream: top and ALA cream: bottom). After 3 hours application, black and white images showed that a lower level of fluorescence (white) of PAP was obtained in MAL-treated area compared with the ALA-treated area.

 

Greater induction of porphyrins has also been obtained with esters of 5-ALA applied to tumor cells in culture.35 Lastly, in contrast to topical application of MAL, topical application of ALA on nude mice skin leads to systemic uptake and enhanced systemic levels of photoactive porphyrins (PAP), including in internal organs[31] (Figure 3). Thus, ALA derivatives such as MAL have different abilities to cross biological barriers.

MAL cream is an oil in water emulsion containing methyl aminolevulinate hydrochloride, equivalent to 168 mg/g of methyl aminolevulinate. Outside the USA, the strength of MAL cream is given as 160 mg/g. In the USA, based on a recommendation by FDA, the labeled strength of MAL cream is 168 mg/g. This reflects a 5% overage, and does not represent a difference in strength. Thus the amount of active ingredient by weight is the same in both cases.

Photosensitization following application of MAL cream occurs through the conversion of MAL to PAP, which accumulate in the skin lesions to which MAL cream has been appled. Photoactive porphyrins are concentrated in the mitochondria of proliferating epithelial cells of lesions through the enzymatic pathway of heme synthesis. When the loaded tissue is illuminated with light of the appropriate excitation wavelength, singlet oxygen is produced which results in mitochondrial damage and cell death. Activation of accumulated intracellular porphyrins is achieved by illumination with broadband light in the range 570-670 nm, which is within the visual spectrum.


Figure 3:         Systemic Absorption of MAL Versus ALA Cream after Topical Application in Mice

 

 

 

 

 

 

 

 

 

 

 

 

 

 


Figure 3: No systemic absorption of MAL after topical application. ALA cream (20%) and MAL cream (20%) was applied to the flank of nude mice and the fluorescence of PAP in the skin was measured at different time points. In ALA treated mice (left panel) the fluorescence (red) was spread to all parts of the mice, while in MAL treated mice (right panel) fluorescence was only observed at the site of application.

 

Selectivity of the treatment for dysplastic lesions of the skin relative to surrounding skin or other tissues is provided by:

·     Application of the cream directly to the lesion;

·     Limited penetration of methyl aminolevulinate in normal skin (see Figure 2);

·     Preferential accumulation of porphyrins in hyperproliferating cells of lesions (see Figure 4);

·     Illumination of the lesion and a thin margin of surrounding tissue only; and

·     Rapid clearance of accumulated porphyrins by photoactivation (photobleaching).


Additional potential advantages of MAL-PDT over other recognized treatments are:

·     Availability on an outpatient basis for simultaneous treatment of several lesions;

·     Improved cosmetic results over current therapies;

·     Repeatability; and

·     No known systemic toxicity or interaction with other medication.

The use of laser as a light source in PDT may be unsatisfactory, since emission spectra do not include the absorption spectra of intracellular porphyrins, which may contribute to cytotoxicity. The CureLightTM BroadBand light source used in the development program of MAL‑PDT (168 mg/g), is easy to manage and less expensive than a laser. The lamp emits red light of the appropriate wavelength band (570 to 670 nm) using a 150-W halogen lamp, and removes infrared light with filters, thus providing an emission spectrum that, unlike laser, includes the absorption spectra of endogenous porphyrins other than PpIX. Red light has better tissue transmission than blue light and therefore achieves photoactivation at a greater depth. The total energy delivered to the lesion is easily controlled and is therefore precise.

Figure 4:         Tumor Selectivity of MAL Cream

 

 

 

 

 

 

 

 

 

 

 

 

 

Figure 4: Tumor selectivity of MAL cream. PAP fluorescence (red) in BCC lesion and normal skin after 3 hours MAL cream application (fluorescence picture left and normal white light picture right).


Treatment of BCCs with MAL-PDT involves 3 stages: lesion preparation, application of MAL cream to the lesion and a rim of surrounding normal skin, and illumination (see Figure 5). All stages should be considered an integral part of the MAL-PDT therapy.

Figure 5:         MAL-PDT Treatment Stages

 


3         overview of preclinical development program

A complete preclinical program has been conducted to support the use of MAL for the treatment of superficial and nodular basal cell carcinoma.

Pharmacology and toxicology studies have been carried out in different animal models including mice, rats, rabbits, Guinea pigs, and minipigs. In vitro models including bacteria, eukaryotic cells, and skin samples have also been used. Skin penetration studies have been performed with human cadaver and rat skin. Most pharmacodynamic and pharmacokinetic studies have investigated the effects of methyl aminolevulinate or MAL cream without photoactivation, while some studies, in particular key toxicology studies, also have assessed the effect of the MAL cream in combination with photoactivating light.

The preclinical development program is summarized in Table 1 through Table 16.

3.1        Pharmacology

Table 1 summarizes the preclinical pharmacology studies. The animal pharmacodynamic studies were conducted to compare the in vitro and in vivo effects of 5-ALA and its methyl ester with respect to production of intracellular PpIX and sensitization of cells to photoactivation—they assessed the time course of PpIX fluorescence and the relationship between PpIX fluorescence and the dose applied.

In in vivo experiments, methyl aminolevulinate administered topically in a cream formulation caused dose-related increases in skin fluorescence, indicating intracellular accumulation of PpIX. The tested dose range was 16 to 160 mg/g. This limitation notwithstanding, the results from the above experiments showed that a plateau of effect was reached with 160 mg/g.

The results of the in vitro experiments showed that esterification of 5-ALA enhanced cell penetration and accumulation of PpIX. The protoporphyrin species induced by methyl aminolevulinate is identical to that induced by 5-ALA based on HPLC on cell extracted with perchloric acid/methanol with fluorescence detection. The formed intracellular porphyrin species were localized as well-defined spots in the cytoplasm. Additionally, a diffuse fluorescence was seen in the entire cytoplasm, while practically no fluorescence was found in the nuclear region. Localization of the protoporphyrin was identical regardless of the precursor administered to the cells.

3.2        Acute Toxicity

Table 2 summarizes the results of the acute toxicity studies. The results of these studies established that methyl aminolevulinate has a low order of single-dose oral and intravenous toxicity in mice and rats. The lowest lethal oral acute dose in mice and rats was greater than 2000 mg/kg. The lowest lethal intravenous dose was 840 mg/kg in mice and 1500 mg/kg in rats. The human (systemic) dose after topical application is estimated to be 100 µg (implying about 1.5 µg/kg). Thus, the lowest lethal dose found in rats is 1,000,000 times greater than the estimated human dose. In addition, systemic application of 30 mg/kg of ALA has been shown to be safe.

3.3        Subchronic, Chronic, and Related Toxicity Studies

Table 3, Table 4, and Table 5 summarize the results of the 2 studies of repeated intravenous administration. The results of these repeated dose studies indicate that the liver is the target organ for high intravenous doses of methyl aminolevulinate in male and female rats. A no adverse effect level (NOAEL) in the rat of 200 mg/kg/day when dosed intravenously for 14 consecutive days predicts a wide margin of safety for the topical administration of single or occasionally repeated doses of methyl aminolevulinate.

3.3.1       Hepatotoxicity

The results of repeated‑dose studies indicated that the liver was the target organ for high IV doses of methyl aminolevulinate hydrochloride in male and female rats. The no‑adverse‑effect level (NOAEL) in rats was 200 mg/kg/day when dosed intravenously for 14 consecutive days. Repeated IV doses of 600 mg/kg for 14 days to rats caused decreased hemoglobin, red blood cell count, and packed cell volume, and increased serum levels of protein and cholesterol. Reduced ALP activity, increased ALT activity, and reduced urinary volumes were also noted. Histopathologic examination revealed cholangitis/pericholangitis in animals of both sexes.

It should be noted that although there were indications of moderate hepatotoxicity in rats following the systemic (IV) administration of high doses of methyl aminolevulinate (600 mg/kg/day), no hepatotoxicity was observed following 200 mg/kg/day. This dose represents more than 400 times the maximum clinical dose applied topically.

Furthermore, studies conducted with rats and minipigs designed to study dermal toxicity after treatment with MAL cream, followed by photoactivation, have not indicated any hepatotoxicity. In the microscopic examination of the collected tissues from the minipig study, no treatment-related findings were seen in the evaluated organs. The inflammatory-degenerative changes recorded in the kidneys, liver, lung, adrenals, and testes were considered incidental findings and occurred at the same degree in both the placebo and the MAL cream group.

Routine monitoring of clinical laboratory parameters in humans was performed in 2 dose‑finding Phase 2 studies (Studies 202/98 and 203/98), a Phase 3 study (Study 205/98), and 2 small exploratory studies (Studies 101/98 and 204/98). No signs of liver toxicity were observed. The results are provided in Section 8.6.

3.4        Dermal Application

Table 6, Table 7, and Table 8 summarize the 3 studies conducted to assess the tolerance for topically applied MAL cream followed by photoactivation in rats and minipigs. The treatment in these studies mimics the clinical treatment situation, except that the treatments were repeated 4 times. Importantly, the studies assessed both local effects and systemic effects. The first study, using rats, investigated a single treatment, the second study investigated a four times repeated treatment at the same skin spot in rats, and the third study tested a four times repeated treatment of the same spot in the minipig. A new treatment of the same spot was not commenced until the lesion from the previous treatment was judged as healed when inspected visually.

Application of MAL cream, in the absence of illumination, caused well-defined erythema, which persisted for a few days after treatment. As expected, when combined with illumination, single applications of MAL cream caused slight to severe erythema and up to moderate edema after each treatment. In addition, central wound formation was observed at most application sites and these wounds persisted, as crust formation, until the next treatment.

Repeated dermal applications of MAL cream followed by photoactivation (light illumination) induced epidermal crusts, epidermal hyperplasia, dermal/epidermal inflammation, dermal hemorrhage, and acute wounds (epidermal/dermal coagulation necrosis).

Additional histopathology evaluations were performed on tissues collected in repeated‑dose dermal toxicology study conducted in minipigs. The following tissues were evaluated: liver, adrenals, brain, heart, kidneys, lungs, ovaries, pituitary, prostate, spleen, testes, thymus, thyroid, and uterus. The results from histopathology of the sampled internal organs were reported in amendments to the original report.

In the main study animals and the recovery animals, the conclusions from the microscopic examination were that no active treatment-related findings were seen in the evaluated internal organs.

3.5        Special Toxicity Studies

Table 9 summarizes the 2 special toxicity studies that were conducted. In the eye irritation study, all animals exhibited some degree of injection of corneal vasculature but differentiation between MAL‑treated and control animals was not possible. Instillation of fluorescein revealed no corneal disruptions in either dosed or control rabbits. Finally, there was no evidence that ambient lighting conditions affected the irritancy or ocular effects of MAL cream.

In the skin sensitization study, methyl aminolevulinate elicited a positive response in 13/20 guinea pigs and inconclusive responses in 5 animals. The results of this experiment indicate that methyl aminolevulinate may cause skin sensitization upon dermal contact.

3.6        Mutagenicity Studies

Table 10 summarizes the mutagenicity studies. The potential for methyl aminolevulinate to induce mutagenicity and/or genotoxicity was assessed through the use of 3 in vitro and 1 in vivo models. In addition to the usual protocols for these experiments the in vitro tests were modified to allow for incorporation of light exposure of methyl aminolevulinate exposed cells.

Methyl aminolevulinate alone or in combination with a microsomal activating system produced no evidence of mutagenic potential in commonly used bacterial strains (TA 98, TA 100, TA 1535, TA 1537, WP2 pKM101, WP2uvrA pKM101 ). When methyl aminolevulinate exposed test systems were exposed to light, unequivocal cytotoxicity was evident, but even at cytotoxic doses there was no evidence of mutagenicity. Similarly, Chinese hamster ovary cells exposed to methyl aminolevulinate in the presence of light (5 or 50 J/cm2) exhibited marked cytotoxicity but no clastogenicity. Intravenously administered methyl aminolevulinate did not induce micronuclei in the bone marrow of rats.

3.7        Reproductive Studies

No study of the potential toxicity of methyl aminolevulinate to the reproductive function or of the potential embryo-fetal or perinatal toxicity has been conducted. This is considered justified since it has been demonstrated that the systemic exposure after topical application of methyl aminolevulinate is negligible.

3.8        Carcinogenicity Studies

No formal Good Laboratory Practice (GLP) study has been conducted to assess the potential of methyl aminolevulinate to cause cancer. This is considered justified because the treatment is only given once or twice, the mutagenicity studies showed negative results, and systemic exposure is negligible.

3.9        Absorption, Distribution, Metabolism, Excretion

Table 11 through Table 16 summarize the preclinical absorption, distribution, metabolism, and excretion (ADME) studies. The metabolites 5-ALA or PpIX were not detected in tissue other than the skin application site after single dose topical application of methyl aminolevulinate to rats (non-abraded skin). Only after repeated dosing with subsequent photoactivation of rats, could slightly elevated levels of 5-ALA be measured in serum. No signs of systemic toxicity were seen.

Use of 14C-methyl aminolevulinate in topical application to rats for 48 hours resulted in 13.1% and 6.4% systemic absorption through abraded and non-abraded skin respectively. The major fraction of this was collected in excreta and the remaining fraction was concentrated to kidney/bladder and intestine content, indicating that it was on its way to be excreted. It was also found that the fraction remaining at the skin application site was 6.3% (abraded) and 8.4% (non-abraded) after 24 hours exposure.

The in vitro study showed that human skin had a much lower permeability for 14C‑methyl aminolevulinate than the rat skin. The systemic absorption through human skin of only 0.26% of the applied dose after 24 hours application, means that only 1.74 mg of a human dose of 672 mg MAL (4 g cream) will be absorbed systemically after this period.

In the clinical situation a 3-hour application period is used. Assuming a 1.6-hour lag phase, this means that only 1.74 mg x (3-1.6)/24 = 0.101 mg ≈ 100 μg (or 1.5 mg/kg) of a human dose of 672 mg MAL (4 g cream) will be absorbed systemically. This amount is considered to be negligible.

It was found in the in vitro penetration study that the fraction of radioactivity forming a depot in the skin was 9.449% for the rat skin after 24 hours exposure. This corresponds well with the findings from the in vivo excretion experiment in which 8.4% of the applied dose was found in the skin.

It is concluded that adequate amounts of methyl aminolevulinate are absorbed into the epidermis of the skin, the site of action of the drug. Adequate local epidermal exposure has been shown, while systemic exposure to methyl aminolevulinate after topical application is negligible.

3.10     Discussion

The results of preclinical toxicology data predicted that methyl aminolevulinate cream 168 mg/g would be safe for topical use by humans. The results of clinical studies are consistent with the preclinical data. As summarized in Section 8, none of the clinical studies have shown any evidence of systemic toxicity. There were few non‑local adverse events, and, although a relationship to treatment could not be ruled out in all cases, it should be noted that a similar frequency of non-local adverse events was observed in the placebo, surgery, and cryotherapy groups. The majority of adverse effects was attributable to expected phototoxicity and occurred during or after illumination. Although most lesions treated in the clinical studies were on the face or scalp, no evidence of ocular toxicity was observed. The potential for methyl aminolevulinate cream 168 mg/g to elicit irritancy and allergenicity was examined further in clinical Studies 107/01, 108/01, and 110/03.

3.11     Conclusions

·     Methyl aminolevulinate acts as a precursor of heme biosynthesis and causes intracellular accumulation of photoactive porphyrins in both in vivo and in vitro models. Accumulated intracellular porphyrins can be used in PDT.

·     Single or repeated, oral, intravenous or topical doses of methyl aminolevulinate were well tolerated by mice, rats, and minipigs indicating a low potential for systemic toxicity. The NOAEL after repeated intravenous administration for 14 consecutive days was 200 mg/kg/day.

·     Single or repeated topical applications of methyl aminolevulinate followed by photoactivation cause clear but reversible dermal lesions in rats and minipigs but with no evidence of systemic toxicity in either species.

·     The pharmacokinetic investigations in animal models have documented that the systemic absorption of methyl aminolevulinate and its metabolites is minimal, and an in vitro model has shown that the human skin is even less permeable to these compounds. The systemic absorption and exposure of humans after dermal treatment is negligible.

·     From the specification of the active pharmaceutical ingredient methyl aminolevulinate and the drug product MAL cream, there are no impurities or degradation products that should exclude the product from the intended use.

·     There is no indication that methyl aminolevulinate or its metabolites are genotoxic, neither with nor without photoactivation.

·     MAL cream is not irritating to the eye, but has been shown in guinea pigs, the potential to cause delayed contact hypersensitivity.

Thus, the results of the preclinical studies show that MAL cream has a high potential for safe therapeutic application in PDT of premalignant and malignant neoplasms of human skin.

 


Table 1:          Pharmacology Studies

Study Title

(Study Report)

Test model

Route of admin.

Dosing

Primary

Pharmacological

Action

Secondary

Pharmacological

Action

Formation of PpIX in murine skin after topical application of cream formulations containing different concentrations of P‑1202

(Report FT-18)

Female Balb/c athymic nude mice

Applied to skin

Creams contained 16, 80 or 160 mg/g of methyl aminolevulinate. A spot of cream was applied to each flank on each mouse.

Methyl aminolevulinate caused dose-related increase in PpIX in skin

None observed

 

Formation of PpIX in murine skin after topical application of P-1202 in different cream formulations

(Report FT-13)

Female Balb/c athymic nude mice

Applied to skin

Five cream formulations each containing 16 or 160 mg/g of methyl aminolevulinate. About 0.5 g of cream was applied to about 2 cm2 on flank

Dose-related increase in fluorescence with maximum effect at about 10 hr

None observed

Comparison of PpIX formation after ALA and ALA methyl ester addition to cell cultures.

(Report FT-40)

Human tumor cells (WiDr and NHIK 3025) and Chinese hamster fibroblasts

Added to medium

1 and 2 mM 5-ALA or methyl aminolevulinate for 4 hr. Irradiation with fluorescent light (15 W/m2)

Methyl aminolevulinate caused more PpIX formation than 5-ALA. No significant amounts of other porphyrins were detected. Cells were sensitized to light.

None observed

 


 

Table 2:          Acute Toxicity Studies

Study Title

(Study Report)

Species

Sex / age

Dose range

(mg/kg bw)

Route of Adm. /

Vehicle

Toxic signs

Lethal doses

(mg/kg bw)

Time to death

Single dose oral toxicity study in the mouse.

(Report 1458/8-1032

Mouse

Males /

5-7 weeks

Females /

5-7 weeks

2000

Oral (gavage) /

purified water

Pilo-erection in 2 males and 3 females

None

Not applicable

Single dose intravenous toxicity study in the mouse.

(Report 1555/003-1032)

Mouse

Males /

6-7 weeks

Females /

6-7 weeks

585 - 2000

Intravenous / physiological saline

Lethargy,
pilo-erection, gasping proneness, tachypnea

840

1000

2000

15 min

Immediately

Immediately

Single dose oral toxicity study in the rat.

(Report 1458/7-1032)

Rat

Males / 6-8 weeks

Females /

6-8 weeks

2000

Oral (gavage) / purified water

None

None

Not applicable

Single dose intravenous toxicity study in the rat.

(Report 1555/002-1032)

Rat

11 males / 7-9 weeks

11 females / 10-11 weeks

1000 – 2000

Intravenous / physiological saline

Lethargy, salivation. Isolated cases of breathing pattern changes, tachypnea, bradypnea, dyspnea, pilo-erection, anogenital soiling

1500

2000

During dosing (<1/2 hour)

Immediately

 


 

Table 3:          Design of Studies for Repeated Intravenous Administration (Studies 1555/7 and 1555/8)

 

Study Title

(Study Report)

Species/
Strain

No. / sex (age)

Doses

Dose schedule

Route of administration

Vehicle

7‑day intravenous dose-range finding toxicity study in the rat (Report 1555/7-D6144)

Rat / Crl:CD.BR

9 males (6 weeks)

9 females (6 weeks)

0, 250, 750 mg/kg/day

Dosed daily for 7 consecutive days

Intravenous

Sterile physiological saline

14‑day intravenous toxicity study in the rat.

(Report 1555/8-D6144)

Rat / Crl:CD.BR

10/sex/dose80 animals used

0, 50, 200, 800 (600)

mg/kg/day

Dosed daily for 14 days then observed for one day after final dose.

Intravenous

Sterile physiological saline

 

Table 4:          Dose-Related Changes After 7-Day Repeated Intravenous Administration (Study 1555/7)

 

Study Title

(Study Report)

Doses

(mg/kg/

day)

Survival

Weight gain

Toxic signs

Hematology (day 6)

 

Clinical chemistry

 

Change in organ wt

Pathological findings

(macroscopic findings)

7‑day intravenous dose-range finding toxicity study in the rat (Report 1555/7-D6144)

0

250

 

 

750

6/6

6/6

 

 

6/6

 

NSC

 

 

NSC

None

Red brown staining of nose and mouth

 

Red brown staining of nose and mouth

 

NSC

 

 

NSC

 

 

 

 

 

Bilirubin levels were significantly elevated (males and females). Decreased levels of urea and BUN (females)

 

T/E: - 10%

 

 

T/E: -13%

Apparent changes showed no trend consistent with a treatment-related effect on any target organ. Such changes included dark foci on the lungs of one male dosed with 750 mg/kg/day and a clear cyst on the kidneys of a second male in this group.

NSC: No significant change; BUN: Blood urea nitrogen; T/E: testes/epididymides (males);
*: no notable change

Table 5:          Dose-Related changes after 14-Day Repeated Intravenous Administration (Study 1555/8)

Study Title

(Study Report)

Doses

(mg/kg/day)

Survival

 

M       F

Weight gain

Toxic signs

Hematology (day 13)

 

Clinical chemistry

 

14‑day intravenous toxicity study in the rat.

(Report 1555/8-D6144)

0

50

200

600

 

 

 

 

 

(800)§

10/10 10/10

10/10 10/10

10/10 10/10

10/10 10/10

 

 

 

 

 

9/10  10/10

 

NSC

NSC

NSC

 

 

 

 

 

NSC

None

None

None

Red brown staining of the mouth, salivation noisy respiration, pilo-erection, ataxia

Labored or noisy respiration, ataxia, bulging eyes, salivation

 

NSC

NSC

Decreased red blood cell counts, hemoglobin and packed cell volumes

 

NSC

NSC

Increased levels of bilirubin, total protein, cholesterol, alkaline phosphatase and alanine transferase

§             Changed to 600 mg/kg/day after death of one male on day 2; NSC: No significant change;

 

Dose-Related changes after 14-Day Repeated Intravenous Administration (Study 1555/8) (Continued)

Study Title

(Study Report)

Doses

(mg/kg/day)

Change in organ wt

 

              

Pathological findings

(macroscopic findings)

14‑day intravenous toxicity study in the rat

(Report 1555/8-D6144)

0

50

200

600

 

 

(800)§

 

AMLW (m) ↑  AMSW (f) ↓

AMLW (m) ↑, AMLW (f) ↑,

AMLW (m) ↑, AMLW (f) ↑,

 

 

None

None

Minor cholangitis/pericholangitis. Possibly due to the finding of enlarged livers (esp. males).

§             Changed to 600 mg/kg/day after death of one male on day 2; AMLW: Adjusted mean liver weight;

               AMSW: Adjusted mean spleen weight; m: males; f: females


 

Table 6:          Study of Single Dermal Application with Photoactivation

Study Title

(Study Report)

Species/
Strain

No. / sex (age)

Doses

Conc.      Duration    Photoact.

Route of admin/

Vehicle

Pathological findings

(macroscopic findings)

Single dose dermal toxicity in the rat with integral photoactivation procedures

(Report 1555/001-1032)

Rat / Crl:CD.BR

55 males (7-9 weeks) 55 females (10-11 weeks)

0

160 mg/g

160 mg/g

16 mg/g

160 mg/g

 

12 hr

12 hr

12 hr

12 hr

36 hr

 

 

200 J/cm2

100 J/cm2

200 J/cm2

100 J/cm2

100 J/cm2

 

 

Dermal

Unguentum Merck

Interim sacrifices were performed on days 3, 8 and 15. No systemic toxicity was found. Dose-related erythema, edema, hyper-keratinization, scab, escar, necrosis and fissuring were observed. Histopathology confirmed inflammation. Healing observed during 15 days.

 

Table 7:          Study of Repeated Dermal Application with Photoactivation

Study Title

(Study Report)

Species/
Strain

No. / sex (age)

Doses

Conc.      Duration      Photoact.

Route of admin.

Schedule

Vehicle

Pathological findings

(macroscopic findings)

Repeated application dermal toxicity study in the rat with integral photoactivation procedure

(Report 1555/005-1032)

Male and female rats, Crl:CD.BR

50 males (10-11 weeks)

50 females (13-15 weeks)

0

160 mg/g

 16 mg/g

 80 mg/g

160 mg/g

24 hours

24 hours

24 hours

24 hours

24 hours

100 J/cm2

  0 J/cm2

100 J/cm2

100 J/cm2

100 J/cm2

 

Dermal

Treatment administered on days 1, 11, 29 and 43 (males) 48 (females)

MAL base cream

No systemic toxicity. Site of application showed treatment dependent erythema, edema, hyperkera-tinization, escar, hemorrhage and bruising

 

 

Table 8:          Study of Repeated Dermal Application with Photoactivation

Study Title

(Study Report)

Species/
Strain

No. / sex (age)

Doses

Conc.    Duration  Photoact.

Route of admin.

Schedule

Vehicle

Pathological findings

(macroscopic findings)

Repeated dose dermal toxicity study with integral photoactivation in minipigs

(Report 35635)

 

Göttingen SPF minipigs

8 males and 8 females

(3-4 months)

0

0

160 mg/g

160 mg/g

3 hours

3 hours

3 hours

3 hours

 0 J/cm2

75 J/cm2

 0 J/cm2

75 J/cm2

 

Dermal

Dermal

Dermal

Dermal

Four doses, 12 to 26 days apart. Animals were observed for 3 or 15 days after final dose, then sacrificed

MAL base cream

 

No evidence of systemic toxicity. MAL cream (no illumination), caused well-defined erythema which persisted for a few days after treatment. When combined with illumination, single applications of MAL cream caused slight to severe erythema and up to moderate edema after each treatment. Repeated dermal applications of MAL cream followed by illumination induced epidermal crusts, epidermal hyperplasia, dermal/epidermal inflammation, dermal hemorrhage, and acute wounds (epidermal/dermal coagulation necrosis). Repeated applications of MAL cream without photoactivation caused a slight chronic dermatitis which was reversible during the recovery period. Thus, both the formulation and light activation cause a local reaction but the reaction is more severe after light activation. Reversible skin lesions were produced.

 


 

Table 9:          Special Studies Conducted to Assess Local Irritancy and Immunostimulation Induced by Methyl Aminolevulinate

 

Study Title

(Study Report)

Species/
Strain

No./sex/grp (Total No.)

Route of Administration

Treatment Regimen

Duration of dosing/observation

Results

Eye irritation in the rabbit

(Report 1555/009-D6144)

New Zealand White Rabbits,

2 females, 7 males

3 animals per group. Totally 9 rabbits

Instillation of cream into conjunctival sac

0.1 ml of placebo or methyl aminolevulinate (168 mg/g) containing cream

Single instillation. Animals maintained in reduced light and ambient light and observed for 72 hours.

No evidence of irritation by methyl aminolevulinate

Skin sensitization study in the Guinea pig.

(Report 1555/004-1032)

Female Guinea Pig/ Dunkin-Hartley

10 females in control group, 20 females in test group

Intradermal injection and dermal application

Animals received intradermal injection on day 1, dermal applications on day 8 and final dermal challenge on day 22.

Dermal response was graded 24 and 48 hours after challenge

Methyl aminolevulinate elicited a positive reaction in 13/20 animals with inconclusive reactions in 5.

 


 

Table 10:        Mutagenicity Studies

Study Title

(Study Report)

Test system

Metabolizing System

Concentrations tested

Contact/ Incubation time

Positive Control

Results

 Reverse mutation in four histidine-requiring strains of S. typhimurium and two tryptophan-requiring strains of E coli.

(Report 1458/11-1052)

Tester strains

TA98, TA100, TA1535, TA1537, WP2 pKM101 and WP2uvrA pKM101.

+/- S9-mix

Maximum dose: 5000 mg/plate

3 days

TA98:2-nitrofluorene

TA100: Na Azide

TA1535: Na Azide

TA1537: 9 aminocridine

WP2pKM101:4-nitroquinoline 1-oxide

WP2 uvrA:2-aminoanthracene.

No evidence of mutagenicity

Reverse mutation in three histidine-requiring strains of S. typhimurium and one tryptophan-requiring strains of E coli in the presence of visible light.

(Report 1458/12-1052)

Tester strains

TA98, TA100, TA1537, WP2pKM101

None

Maximum dose: 5000 mg/ml. Maximum light dose: 100 J/cm2

Preincubation 3 hr, irradiation with up to 100 J/cm2 and incubation for 3 days after removal of test compound

TA98:2-nitrofluorene

TA100: 4-nitroquinoline 1-oxide

TA1537: ICR-191

WP2pKM101:N-methyl-N'-nitro-N-nitrosoguanidine and 8-methoxypsoralen.

 

Clear evidence of phototoxicity but no photomutagenic activity

Induction of chromosome aberrations in cultured Chinese hamster ovary cells in the presence of visible light.

(Report 1458/13-D5140)

Chinese hamster ovary (CHO) cells

None

Maximum concentration: 1816 mg/ml. Light dose: 5 or 50 J/cm2

Preincubation 4 hr, irradiation with up to 50 J/cm2 and 16 hr recovery after removal of test compound.

4-nintroquinoline 1-oxide and 8-methoxypsoralen.

Marked cytotoxicity at highest light dose. No chromosomal aberrations or clastogenic effects observed.

Induction of micronuclei in bone marrow of treated rats.

(Report 1458/24-D5140)

Male Rats/Crl:HanWist (Glx:BRL)BR

N/A

250, 500 and 1000 mg/kg administered intravenously on two consecutive days.

Samples taken 24-hours after second dose

Cyclophosphamide, 40 mg/kg, intravenously 24-hours prior to sample collection

Unequivocal signs of cytotoxicity in high dose methyl aminolevulinate rats. No evidence of micronuclei induction.


 

Table 11:        Skin Fluorescence After Systemic Administration

Study Title

Study Report

Species/
Strain

Animals/ group

(Total)

Route of administration

Dose

Compound Measured

(Method)

Results

ALA and ALA-esters: Skin build-up after IV or IP injection.

(Report A-1.2A)

Female Mice, Balb/c athymic nude

5 per dose, 30 animals used

Intravenous or intraperitoneal

50, 150, or 250 mg/kg

PpIX formation in skin monitored by its fluorescence at 632 nm

5-ALA produced greater fluorescence than the esters. Fluorescence appeared earlier and with a sharper peak after 5-ALA administration than after administration of methyl aminolevulinate.

PpIX formation n mouse skin after administration of P-1202. Oral vs. intraperitoneal administration.

(ReportFT-11)

Mice, Balb/c nu/nu nude

5 per group, 20 animals used

Oral or intraperitoneal

1.5 mmole/kg

( 250 mg/kg ALA and 272 mg/kg methyl amino-levulinate)

PpIX formation in skin monitored by its fluorescence at 632 nm

ALA produced significantly more and long-lasting fluorescence than did the ester.

 

Table 12:        Blood Levels of 5-ALA and PpIX After Single Dermal Application

Study Title

(Study Report)

Species/
Strain

No. / sex (age)

Doses

Conc.      Duration      Photoact.

5-ALA levels*

 

Results (PpIX levels*)

Single dose dermal toxicity in the rat with integral photoactivation procedures

(Report 1555/001-1032)

Rat / Crl:CD.BR

55 males (7-9 weeks) 55 females (10-11 weeks)

0

160 mg/g

160 mg/g

16 mg/g

160 mg/g

 

12 hr

12 hr

12 hr

12 hr

36 hr

 

 

200 J/cm2

100 J/cm2

200 J/cm2

100 J/cm2

100 J/cm2

 

 

 

 

Negligible for all groups

 

 

Negligible for all groups

* Blood sample taken immediately after removal of cream, i.e. before photoactivation


 

Table 13:        Blood Levels of 5-ALA and PpIX After Repeated Dermal Application with Integral Photoactivation

Study Title

(Study Report)

Species/
Strain

No. / sex (age)

           Dosing

  Conc     Duration     Photoact.

5-ALA (1)*

ng/ml

5-ALA (4)*

ng/ml

PpIX (1)*

ng/ml

PpIX (4)*

ng

Repeated application dermal toxicity study in the rat with integral photoactivation procedure

(Report 1555/005-1032)

Male and female rats, Crl:CD.BR

50 males (10-11 weeks)

50 females (13-15 weeks)

   0            24 hours       100 J/cm2

160 mg/g  24 hours       100 J/cm2

 16 mg/g   24 hours       100 J/cm2

 80 mg/g   24 hours       100 J/cm2

160 mg/g  24 hours       100 J/cm2

14 ± 2

28 ± 12

ND

ND

23 ± 7

ND**

250 ± 125

ND

ND

179 ± 162

 

ND

15 ± 18

ND

ND

20 ± 28

ND

10 ± 4

ND

ND

27 ± 32

(1): Immediately after cream removal - first treatment; (4): Immediately after cream removal - fourth treatment; * data shown as median ± SD; ** Not determined

 

Table 14:        Skin Localization After Dermal Application          

Study type

(Study Report)

Species/
Strain

Animals/ group

(Total)

Route of administration

Dose

Compound Measured

(Method)

Results

Biolocalization of 5-ALA and ALA methyl ester induced porphyrins in normal mouse skin

(Report FT-39)

F Balb/c nu/nu athymic nude mice

5 mice /group; total 20

Topical application of cream containing: a) 148 mg/g ALA or b) 160 mg/g methyl aminolevulinate

0.1 g cream applied onto a 2.25 cm2 area

Fluorescence microscopy of frozen sections taken from treated mouse skin samples

No fluorescence in control. Porphyrin fluorescence noted in epidermis, epithelial hair follicles and sebaceous glands but not dermis. Fluorescence intensity increased with time with max seen at 6 hours post treatment.

 


 

Table 15:        Absorption, Distribution and Excretion after Dermal Application

Study type

(Study Report)

Species/ Strain

Animals/ group

(Total)

Route of administration

Dose

Compound Measured

(Method)

Results

Quantitative whole-body autoradiography and excretion of radioactivity following topical administration of

14C-P-1202 cream to the rat

(Report1555/10-D11407)

Male albino rats

3 /group; total 12

Topical administration of 14C‑P-1202 to rats with abraded or non‑abraded skin.

300 mg cream / animal (48 mg

of methyl amino-levulinate per animal)

Whole body autoradiography. (Animals sacrificed at 3,8, 24 hours post-dose)

Absorption / Excretion. Animals sacrificed at 48 hours post-dose

Tissue radioactivity was well distributed. Conc. low at all sampling times.

 

 

 

 

Abraded: 10% of admin radioactivity recovered in excreta (6.5% in urine) and 3% in carcass for total of 13% recovery.

Non-Abraded: 4.5% of admin radioactivity recovered in excreta (3% in urine) and 2% in carcass for total of 6.4% recovery.

 

 

Table 16:        In Vitro Skin Penetration

Study type

(Study Report)

Species/
Strain

Animals/ group

(Total)

Route of admin.

Dose

Compound Measured

(Method)

Results

14C-P-1202 Cream: Rates of penetration through human and rat skin using a static in vitro system.

(Report 1555/13)

Human cadaver back skin and Sprague-Dawley dorso-lumbar skin samples

N/A

 

Topical

(Penetration of 14C through excised skin)

Cream containing 48 mg/g

14C-methyl aminolevulinate applied to the skin for 24 hours

Quantitated 14C in receptor fluid and skin.

Approximately 10-fold more 14C penetrated rat skin than human skin. After 24 hours, 2.097% and 0.26% of the applied dose penetrated rat and human skin, respectively. Furthermore, 9.449% and 4.9% of the dose formed a depot in rat and human skin, respectively.


4         Overview of clinical development program

The New Drug Application (NDA) for photodynamic therapy (PDT) with MAL cream for use in basal cell carcinoma (BCC) was filed with the Food and Drug Administration (FDA) on 21 February 2003 (NDA 21-756).

The development program for MAL-PDT (Figure 6 and Figure 7) has been designed to include a wide spectrum of BCC disease, including low-risk and high-risk superficial and nodular BCC and includes placebo- and active-controlled studies.

The program has focused on developing an alternative treatment for BCC that meets the clinical goals of tumor removal, tissue preservation, and cosmesis. Prior to the initiation of the clinical trials, a multifactorial program was conducted to determine the relationship between dose (concentration of the applied cream), duration of exposure to the cream, and the duration of exposure to the light activation. These data were required for the design of the clinical trials for the use of MAL-PDT in the treatment of both actinic keratosis (AK), subject to a separate application, and BCC. With this information, it was then possible to design clinical trials to evaluate the safety and efficacy of MAL-PDT.

The Phase III program was comprised of 6 studies as follows:

·       Two double-blind, randomized, placebo-controlled trials in patients with low-risk nodular lesions (Studies 307/00 and 308/00);

·       One open, randomized, controlled trial with simple surgical excision as comparator in patients with low-risk nodular lesions (Study 303/99);

·       One open, randomized, controlled trial with cryotherapy as comparator in patients with low-risk superficial lesions (Study 304/99); and

·       Two uncontrolled studies in high-risk patients unsuitable for conventional therapy (Studies 205/98 and 310/00).

As outlined in Figure 6, this program was designed to demonstrate efficacy and safety for treatment with MAL-PDT in 2 distinct BCC populations, namely superficial and nodular low-risk and high-risk BCC.

These studies confirm that MAL-PDT is safe and effective in meeting the treatment goals of tumor removal, tissue preservation, and cosmesis in low-risk and high-risk superficial and nodular BCC.

The integrated summary of safety (ISS) for the BCC application focused primarily on the results of placebo‑controlled and active-controlled Phase III studies in patients with primary nodular and superficial BCC and secondarily on the results of studies in BCC patients unsuitable for conventional therapy due to potential morbidity or poor cosmetic outcome (high-risk patients). Additional safety data for patients with actinic keratosis (AK), a compassionate use program (Study 001/97), and data for other studies were also included to present a complete assessment of the safety profile of PDT with MAL cream (MAL-PDT).

A separate NDA for PDT with MAL cream for use in AK was filed with FDA on 29 September 2001 (NDA 21-415) with a 120-day Safety Update provided on 17 January 2002. A 120-day Safety Update for the BCC indication was submitted on July 16, 2003.

Figure 6:         Phase III Clinical Development Program for BCC

 

 

 

 

 

 

 

 

 

 

 

 

 


References: Randle et al.,16 Swanson et al.,30 and Martinez et al.20

 

Figure 7 provides a more detailed overview of the overall clinical development program for MAL-PDT in BCC. The designs of these studies are summarized in Table 17.

Studies 202/98, 301/99, 302/99, 305/99, and 306/99 were conducted for the AK indication but were included in the BCC ISS submission to support safety. The other studies (101/97, 206/98, 203/98, 205/98, 310/00, 303/99, 304/99, 307/00, and 308/00) were included in the ISE submission for BCC to support efficacy and safety.

Figure 7:         Clinical Development of MAL-PDT in BCC

Number of patients = number of treated patients. Pts = patients; PAP = photoactive porphyrins; comp = comparator; fluor = fluorescence; cryo = cryotherapy; prim =primary; sup = superficial.

* In ISS database and Update pooled database; § Submitted under an IND (#59,756 for Study 306/99 [AK] and #59,221 for Studies 307/00 and 308/00 [BCC]).


 

Table 17:        Table of Studies in the ISS

 

Study Number

Start Date/

End Date

Report Status

Country/
Coordinating
Investigator

Population Studied

Design

Type of Control

Blind

Dose(s) and Frequency of Dosing

Treatment Duration (does not include follow-up period)

No. Pts. Treated

Age range (mean)

(years)

Fitzpatrick skin type

Sex; Race (Caucasian, Non‑Caucasian Unknown)

 

Studies in Basal Cell Carcinoma

 

Placebo-Controlled, Phase III

PC T307/00

Dec 2000 to April 2002

Report July 2002

US

 

Tope

Primary nodular BCC

Phase III, double-blind, randomized, parallel-group, multicenter

Methyl aminolevulinate cream 168 mg/g for 3 h with light dose of 75 J/cm2 (wavelength 570 to 670 nm)

2 treatments, 7 days apart; if partial response at 3‑month follow‑up, another treatment cycle was given; 6 months after last PDT all treated areas were excised for histological examination of response

65

65 (28-88)

Methyl aminolevulinate cream: 62 (28-88)

Placebo: 67 (39-88)

 

Type I: 19 (29%)

Type II: 32 (49%)

Type ³III: 14 (22%)

50 M, 15 F

65 C

 

Methyl aminolevulinate cream: 25 M, 8 F

Placebo

25 M, 7 F

 

PC T308/00

October 2000 to September 2002

Report November 2002

Australia

 

Foley

Primary nodular BCC

Phase III, double-blind, randomized, parallel-group, multicenter

Methyl aminolevulinate cream 168 mg/g for 3 h with light dose of 75 J/cm2 (wavelength 570 to 670 nm)

2 treatments, 7 days apart; if partial response at 3‑month follow‑up, another treatment cycle was given; 6 months after last PDT all treated areas were excised for histological examination of response

66

68 (40-88)

Methyl aminolevulinate cream: 70 (48-87)

Placebo: 66 (40-88)

 

Type I: 27 (41%)

Type II: 22 (33%)

Type ³III: 17 (26%)

49 M, 17 F

66 C

 

Methyl aminolevulinate cream:

22 M, 11 F

Placebo:

27 M, 6 F

 

 

Active-Controlled, Phase III

PC T303/99

ongoing

Reports

Initial – April 2002

3 m – April 2002

12 m – April 2002

24 m – November 2002

UK, France, Sweden, Norway, Netherlands, Austria

 

Rhodes (UK)

Primary nodular BCC

Phase III, open, randomized, parallel-group, multicenter

Methyl aminolevulinate cream 168 mg/g for 3 h with light dose of 75 J/cm2 (wavelength 570 to 670 nm)

 

Surgical excision was performed according to the investigator’s routine with 5‑mm margins

2 treatments, 7 days apart; if treatment failure at 3‑month follow‑up, another treatment cycle was given or the lesion was surgically excised

101

38‑95 (68)

 

Methyl aminolevulinate cream: 40-95 (69)

Surg: 38-82 (67)

 

Type I: 8 (8%)

Type II: 47 (47%)

Type ³III: 46 (46%)

 

61 M, 40 F,

100 C, 1 other,

 

Methyl aminolevulinate cream: 32 M, 20 F

Surg:

29 M, 20 F

 

 

PC T304/99

ongoing

Reports

Initial – May 2001

12 m – November 2002

24 m – November 2002

France, Italy, Sweden, UK, Belgium, Finland, Austria

 

Basset‑Seguin (France)

Primary superficial BCC

Phase III, open, randomized, parallel-group, multicenter

Methyl aminolevulinate cream: 168 mg/g for 3 h with light dose of 75 J/cm2 (wavelength 570 to 670 nm)

 

Cryotherapy: standard liquid nitrogen spray;

Two freeze thaw cycles

1 treatment; if treatment failure at 3‑month follow‑up, a treatment cycle was given

Methyl aminolevulinate cream: Second cycle was 2 treatments 1 week apart

Cryotherapy: Second cycle same as first

118

25‑90 (64)

 

Methyl aminolevulinate cream: 25‑87 (63)

Cryo: 38‑90 (64)

 

Type I: 6 (5%)

Type II: 71 (60%)

Type ³III: 41 (34%)

70 M, 48 F

118 C

 

Methyl aminolevulinate cream: 40 M, 20 F

Cryo: 30 M, 28 F

 

 

 

Unsuitable for Conventional Therapy

PC T205/98

ongoing

Reports

Initial – December 2000

12 m – December 2000

24 m – June 2002

Sweden, Norway, UK, Denmark, Austria, Germany, Netherlands

 

Larkö (Sweden)

Superficial and nodular BCC lesion unsuitable for traditional therapy due to possible morbidity or poor cosmetic outcome

Phase II, open, non‑-comparative, multicenter

Methyl aminolevulinate cream 168 mg/g for 3 h with light dose of 75 J/cm2 (wavelength 570 to 670 nm)

2 treatments, 7 days apart; if treatment failure at 3‑month follow-up, or partial response at 6-month follow-up, another treatment cycle was given
Methyl aminolevulinate cream applied 3 h before illumination

94

 

32-93 (68)

 

Fitzpatrick skin type not assessed

57 M, 37 F

94 C

 

PC T310/00

ongoing

Reports

Initial – January 2002

12 m – September 2002

Australia

 

Vinciullo

Superficial and nodular BCC lesion unsuitable for traditional therapy due to possible morbidity or poor cosmetic outcome

Phase III, open, non‑randomized, non-comparative, multicenter

Methyl aminolevulinate cream 168 mg/g for 3 h with light dose of 75 J/cm2 (wavelength 570 to 670 nm)

2 treatments, 7 days apart; if treatment failure at 3‑month follow‑up, another treatment cycle was given

Methyl aminolevulinate cream applied 3 h before illumination

102

 

26-91 (64)

 

Type I: 29 (28%)

Type II: 46 (45%)

Type ³III: 27 (27%)

66M, 36F

102 C

 

Phase I

 

PC T101/97

June 1997 to October 1998

Norway

 

Warloe

Nodular BCC

Phase I-II, open, single-center PK study

Each patient received 3 concentrations of Methyl aminolevulinate cream, 16 mg/g, 80 mg/g, and 160 or 168 mg/g, for either 3 or 18 h. Lesion biopsy was taken to determine penetration depth of active ingredient. Lesion then illuminated with light dose of 75 J/cm2

Single treatment

16

3 hours: mean 67 years

18 hours: mean 72 years

Fitzpatrick skin type not assessed

11 M, 5 F

16 U

 

 

Dose-Ranging, Phase II

PC T203/98

ongoing

Reports

Initial – January 2001

12 m – June 2001

24 m – June 2002

Final (36 m) expected Feb 2003

Norway, Sweden, Finland, Switzerland, Netherlands, France

 

Basset-Séguin (France)

Primary BCC

Phase I-II, open, randomized, parallel-group, multicenter

Methyl aminolevulinate cream 168 mg/g for 1, 3, 5, or 18 h, with light dose of 75 J/cm2 (wavelength 570 to 670 nm)

1 or 2 treatments, cream on the skin 1, 3, 5, or 18 hours before illumination

141

34 for 1 h treatment

36 for 3 h treatment

35 for 5 h treatment

36 for 18 h treatment

 

33-93 (64)

 

Fitzpatrick skin type not assessed

76 M, 65 F

141 C

 

 

Studies in Actinic Keratosis

 

Placebo-Controlled, Phase III

 

PC T306/99

Jun 2000 to Feb 2001

Final

US

 

Pariser

AK

Thin to moderate AK lesions of the face and scalp

4 to 10 lesions per patient

 

Phase III, randomized, double-blind, placebo-controlled, parallel-group, multicenter

Two treatments, 7 days apart

Methyl aminolevulinate cream 168 mg/g or placebo for 3 h, with light dose of 75 J/cm2 (wavelength 570 to 670 nm)

Two treatments, 7 days apart

80

31-84 (65)

 

Methyl aminolevulinate cream: 31-84 (64)

Placebo: 39-84 (67)

70 M, 10 F

80 C

 

Methyl aminolevulinate cream: 36 M, 6 F

Placebo: 34 M, 4 F

 

PC T305/99

Mar 2000 to Dec 2000

Final

Australia

 

Foley

Thin to moderate AK lesions of the face and scalp

Unlimited number of lesions

Phase III, randomized, parallel-group, multicenter, comparative vs. cryotherapy and placebo

Open for Methyl aminolevulinate cream vs cryotherapy; double‑blind for Methyl aminolevulinate cream vs. placebo

Two treatments, 7 days apart

Methyl aminolevulinate cream 168 mg/g or placebo for 3 h with light dose of 75 J/cm2 (wavelength 570 to 670 nm)

Cryotherapy: liquid nitrogen spray; 1 freeze-thaw cycle

Two treatments, 7 days apart (for Methyl aminolevulinate cream)

1 treatment (for cryotherapy)

200

33-89 (64)

 

Methyl aminolevulinate cream: 33-86 (64)

Placebo: 49-89 (66)

Cryo: 38-86 (65)

119 M, 81 F

200 C

 

Methyl aminolevulinate cream: 49 M, 39 F

Placebo: 16 M, 7 F

Cryo: 54 M, 35 F

 

PC T302/99

Jun 1999 to Jan 2000

Final

Denmark, Norway

 

Bjerring (Denmark)

AK Unlimited number of lesions

Phase III, stratified, randomized, double-blind, placebo-controlled, parallel-group, multicenter

Methyl aminolevulinate cream 168 mg/g or placebo for 3 h, with light dose of 75 J/cm2 (wavelength 570 to 670 nm)

Single treatment for lesions on face and scalp

Second treatment after 1 week for lesions at other locations

38 treated

39 included in safety population

43-87 (68)

25 M, 14F

39 C

 

 

Active-Controlled, Phase III

 

PC T301/99

Apr 1999 to Nov 1999

Final

Switzerland, Germany, Austria, Italy, Netherlands

 

Braathen (Switzerland)

AK

1-10 lesions

Phase III, open, randomized, parallel‑group, multicenter, comparative vs. cryotherapy

Methyl aminolevulinate cream: 168 mg/g or placebo for 3 h with light dose of 75 J/cm2 (wavelength 570 to 670 nm)

Cryotherapy: standard liquid nitrogen spray

Two freeze thaw cycles (single session)

Methyl aminolevulinate cream:

Single treatment for lesions on face and scalp

Second treatment after 1 week for lesions at other locations

Cryotherapy: 2 cycles in a single session

Follow-up 3 months after treatment

202

42-89 (71)

 

Methyl aminolevulinate cream: 42-88 (71)

Cryo: 45-89 (72)

124 M, 78 F

202 C

 

Methyl aminolevulinate cream: 66 M, 36 F

Cryo: 58 M, 42 F

 

PC T311/01

ongoing

Sweden

 

Tarstedt

AK

1-10 mild to moderate lesions on face or scalp

Phase III, open, randomized, parallel-group, , multicenter

Methyl aminolevulinate cream 168 mg/g for 3 h, with light dose of 37 J/cm2 (wavelength 620 to 650 nm)

1 treatment; second treatment 3 months after first, if non‑CR

or

2 treatments, 7 days apart

Not available

Not available

 

Uncontrolled, Phase I and Phase II

 

PC T204/98

Nov 1998 to May 2000

Final

Norway

 

Christensen

AK

Unlimited number of lesions

Phase II, open, randomized, within-patient controlled, single-center, comparative vs. Efudix®

Methyl aminolevulinate cream 168 mg/g for 3 h with light dose of 5 J/cm2 (wavelength 420 nm)

Efudix® applied twice daily for 3 weeks

Methyl aminolevulinate cream repeated at 3 months if non‑CR; light dose of 75 J/cm2 (wavelength 570-670 nm)

Methyl aminolevulinate cream: 1 treatment, second treatment at 3 months after first, if non‑CR

Efudix®: 3 weeks

 

12

59-82 (72)

10 M, 2 F

12 C

 

PC T202/98

Aug 1998 to Mar 2000

Final and 12‑month follow‑up report

Switzerland, Norway, Netherlands,

Sweden,

Finland,

Germany

 

Braathen (Switzerland)

AK

Unlimited number of lesions

Phase I/II, open, randomized, parallel-group, multicenter, dose‑finding

Methyl aminolevulinate cream 80 or 168 mg/g for 1 or 3 h with light dose of 75 J/cm2 (wavelength 570 to 670 nm)

1 treatment; second treatment at 2 or 3 months after first, if non‑CR

 

112

43-91 (73)

 

1 h, 80 mg/g: 55‑91 (75)

1 h, 168 mg/g: 43‑84 (70)

3 h, 80 mg/g: 58‑90 (74)

3 h, 168 mg/g: 46‑85 (73)

63 M, 49 F

112 C

 

1 h, 80 mg/g: 17 M, 8 F

1 h, 168 mg/g: 12 M, 16 F

3 h, 80 mg/g: 16 M, 13 F

3 h, 168 mg/g: 18 M, 12 F

 

Studies in BCC and AK

 

Phase II

 

PC T206/98

Sep 1998 to Apr 1999

Final

Norway

 

Giercksky

Superficial BCC, at least 3 lesions,

or AK, at least 4 moderately thick lesions

Phase I-II, randomized, double-blind, placebo-controlled, single-center

Methyl aminolevulinate cream 16, 80, or 168 mg/g or placebo cream for 28 h with light dose of 75 J/cm2 (wavelength 570-670 nm)

 

Single treatment

15

58-89 (76)

 

10 M, 5 F

15 U

 

Studies in Other Indications

 

PC T001/97

Sep 1997 to Dec 1999

Interim report

Norway

 

Warloe

BCC, AK, and other non-melanoma skin cancers

Unlimited number of lesions

Prospective, open, single‑center compassionate use during Phase I-III studies

Methyl aminolevulinate cream 168 mg/g with light dose of 25 to 200 J/cm2

Varied. 85% the lesions had 1 treatment, but others had up to 5 treatments.

1012 to date.

14-98 (68)

Not stated

 

PC T208/98

Jul 1999 to Feb 2001

Final

Denmark

 

Wulf

Transplant recipients, using immuno­suppresive medication, with AK. 4‑20 lesions per patient.

Phase II, open, randomized, within-patient untreated controlled, 2‑center

Methyl aminolevulinate cream 168 mg/g for 3 h with light dose of 75 J/cm2 (wavelength 570-670 nm)

 

Single treatment at study start. In a subgroup of patients, 1 additional cycle, comprising two treatment sessions 1 week apart, at Month 4.

27

32-75 (57)

17 M, 10 F

27 C

 

PC T211/00

ongoing

Germany

 

Fritsch

BCC

Photodynamic diagnosis of

at least 10 superficial and nodular lesions, eligible for surgical excision

Phase II, within-patient controlled, dose-ranging

Methyl aminolevulinate cream 168 mg/g for 3, 5 and 24 h with light dose of 5 J/cm2 (wavelength 370-400 nm)

24‑hour application

Not available

Not available

 

PC T309/00

ongoing

Scotland

 

Morton

Bowen’s disease

Phase III, randomized, placebo- and active-controlled, multicenter

Methyl aminolevulinate cream 168 mg/g or placebo for 3 h with light dose of 75 J/cm2 (wavelength 570-670 nm)

Methyl aminolevulinate cream and placebo:

2 treatments, 7 days apart; another treatment cycle if non‑CR

Cryotherapy: Single treatment; second treatment if non‑CR

5-Fluorouracil: Cream applied for 4 weeks; second 4‑week treatment if non‑CR

Not available

Not available

 

Studies in Healthy Volunteers

 

PC T107/01

Apr 2001

Final

US

 

Maibach

Healthy subjects

Phase I/II, double-blind, within-subject vehicle–controlled, randomized, single-center acute skin irritancy study

Methyl aminolevulinate cream 168 mg/g and placebo for 24 h with no light therapy

Cream on the skin for 24 hours

12

41-80 (61)

4 M, 8 F

9 C, 2 NC, 1 U

 

PC T108/01

Jun to Jul 2001

Final

US

 

Maibach

Healthy subjects

Phase I/II, double-blind, within-subject vehicle-controlled, randomized, single-center cumulative skin irritancy and sensitization study

Methyl aminolevulinate cream 168 mg/g and placebo with no light therapy

5 days weekly for 2 weeks. 3 weeks later, 48–hour cream application, and 3 weeks thereafter a 48‑hour re-test.

25

32-83 (58)

12M, 13F

24 C, 1 U

 

PC T212/00

ongoing

Germany

 

Szeimies

Healthy subjects

Phase II, randomized, within-subject controlled

Methyl aminolevulinate cream 168 mg/g or cream containing 20% ALA for 5 h with light dose of 75 J/cm2 (wavelength 580-740 nm)

Up to 24‑hour application

Not available

Not available

 

PC T214/01

Feb to Jun 2002

Final

Norway

 

Warloe

Healthy subjects

Phase II, double-blind, within-subject controlled pharmacokinetic study

Phase I: Methyl aminolevulinate cream 168 mg/g and placebo cream for 3 h Phase II and III:

Methyl aminolevulinate cream 168 mg/g and placebo cream for 3 h with light dose of 50 J/cm2 (wavelength 570-670 nm)

No treatment.

 

3‑hour application in all 3 phases.

16

 

20-30 (25)

 

Type I: 1 (6%)

Type II: 6 (38%)

Type III: 9 (56%)

14M, 2F

16 C

 

 


5         Clinical pharmacology

5.1        Photoactive Porphyrin Formation

MAL cream contains methyl aminolevulinate, which is an ester of 5‑aminolevulinic acid (5‑ALA), an endogenous early precursor in the biosynthesis of heme (see Figure 8). 5‑ALA is formed in the mitochondria from glycine and succinyl coenzyme A by the enzyme 5‑aminolevulinic synthase.[32] Two molecules of 5-ALA are then condensed to form the first intermediate, porphobilinogen. In mammals, the heme synthesis pathway occurs in the mitochondria and in the cytosol and takes place in all nucleated cells.

The heme synthesis pathway is regulated by an inhibitory action of heme on the synthesis of 5‑ALA. Therefore, the flux regulation of the heme synthesis pathway can be overruled by supplying exogenous 5-ALA or derivatives thereof, for example methyl aminolevulinate. Since the formation of heme from protoporphyrin IX (PpIX) is also regulated, addition of 5-ALA or derivatives thereof will lead to the accumulation of photoactive porphyrins (PAPs) including PpIX. PAPs are photoactive, fluorescing compounds. Upon light activation of PAPs in the presence of oxygen, singlet oxygen is formed, which causes damage to cellular components, in particular the mitochondria.

 

Figure 8:         Biosynthetic Pathway of Heme in the Cell Mitochondria

 

The intracellular accumulation of PAPs such as PpIX can be measured directly by virtue of their fluorescence. The rate of 5-ALA/5-ALA ester-induced porphyrin synthesis has been shown to be higher in malignant and premalignant cells and tissues than in their normal counterparts.31 Furthermore, fluorescence was shown to be more selectively localized in tumor cells after application of methyl aminolevulinate than after 5-ALA treatment.[33] This greater selectivity is a desirable property with regard to both efficacy and safety since normal skin and other tissues are unaffected.

These observed differences in selectivity are not fully understood and can only be explained partly; they may be due to differences in tissue penetration and distribution, in cellular uptake mechanism, and activation of the heme synthesis enzymes. Furthermore, a topically applied compound has to penetrate the tissue and diffuse through epidermal layers. A more lipophilic agent than 5-ALA is likely to penetrate deeper. It has been shown that 5‑ALA‑induced PpIX formation is often limited to superficial tissue.[34] Using the partition coefficient as a measure for lipophilicity, it has been shown that methyl aminolevulinate seems to penetrate twice as efficiently as 5-ALA into the skin lesions.[35]

There is limited knowledge about the cellular uptake mechanism for methyl aminolevulinate. However, methyl aminolevulinate seems to have a different uptake mechanism from 5-ALA, and this can be one explanation for the difference in selectivity. In contrast to uptake of 5-ALA, uptake of methyl aminolevulinate into a human colon adenocarcinoma cell line has been shown to involve transporters of non-polar amino acids, and it does not seem to be taken up by system BETA transporters.[36],[37]

In summary, methyl aminolevulinate is selectively absorbed by the lesion and is subsequently converted to PAPs in the mitochondria of proliferating epithelial cells. PAPs are activated by light of the appropriate wavelength. For MAL-PDT, red light in the range 570 to 670 nm is used, which is within the visual spectrum. Upon activation of light in the presence of oxygen, singlet oxygen is formed which causes damage to intracellular compartments, in particular the mitochondria, leading to cell death possibly by apoptosis.[38] In addition, inhibition of mitochondrial dehydrogenase, reduced respiration, and mitochondrial swelling have been reported.

5.2        Systemic Absorption

An in vitro study showed that human skin had a much lower permeability for 14C‑methyl aminolevulinate than rat skin. The systemic absorption through human skin was only 0.26% of the applied dose after a 24‑hour application. The penetration was linear after a lag period of 1.6 hours. The systemic absorption through human skin of only 0.26% of the applied dose after a 24‑hour application means that if a very large human dose of 1680 mg (10 g methyl aminolevulinate cream) were used, only 4.37 mg would be absorbed systemically after a 24‑hour application time. However, in a clinical setting, an application time of only 3 hours is used. Therefore, assuming a 1.6‑hour lag phase, 4.37 mg x (3‑1.6)/24 = 0.250 mg = 250 mg of the large human dose of 1.68 g methyl aminolevulinate (from a topically applied dose of 10 g of methyl aminolevulinate cream) will be absorbed systemically. This amount is considered to be negligible and is consistent with the observations described in the preclinical safety section (see Section 3), including that no systemic toxicity has been observed after single and repeated topical application of cream MAL cream.

The pharmacokinetics of methyl aminolevulinate after IV or oral administration was not investigated in humans, because this type of study was not considered appropriate for a topical product such as methyl aminolevulinate cream 168 mg/g.

Negligible systemic exposure is also expected because of the nature of the lesions being treated. Both AK and BCC lesions are tumors of the epidermis and the basement membrane is generally intact.[39],[40] Since methyl aminolevulinate cream 168 mg/g is applied only to the lesion and a small rim of surrounding skin, it is unlikely that substantial quantities of drug penetrate the basement membrane and gain access to the vascular dermis and hence the systemic circulation.

5.3        Selection of Dose Regimen for Pivotal Studies

Treatment of BCC with MAL-PDT is comprised of several components. The dose of MAL-PDT is dependent on the concentration of MAL cream, the length of time that the cream is applied to the skin and the light dose (ie, fluence) delivered in the PDT. The optimal dose of MAL and light as well as application time were ascertained in Phase I and II studies, described below.

5.3.1       Concentration and Application Time of MAL Cream

The following factors were taken into account in selecting the optimum concentration of cream and the duration of its application prior to illumination:

·       Local pharmacokinetics, including depth and surface fluorescence of the fluorescent photoactive porphyrins in lesions and normal surrounding skin after application of cream in various concentrations of methyl aminolevulinate hydrochloride as demonstrated in Studies 101/97 and 206/98. Fluorescence depth, intensity of surface fluorescence, and ratio of fluorescence in diseased/non-diseased tissue (selectivity) were all studied as surrogate markers of efficacy;

·       The response rate of BCC lesions and the safety of patients in Study 203/98 in which MAL cream was applied for different durations prior to illumination.

In addition, patient convenience and acceptability were taken into account, so that the duration of application was to be the minimum consistent with the best outcomes to be obtained in the clinical trials.


5.3.2       Study 101/97

An open, exploratory, (Phase I/II) study of P-1202 (MAL) 160 mg/g cream in patients with nodular basal cell carcinoma

Objectives, Design, and Methods

The primary objective was to determine the optimal MAL cream concentration and duration of application for treating nodular BCC lesions based on the formation of PAPs in the lesion. Six dosage regimens were tested consisting of MAL cream of 3 different strengths (16, 80, or 160 mg/g methyl aminolevulinate) each applied using 2 different application times (3 h or 18 h). Secondary objectives were to determine the safety, tolerability and response rate.

The study was conducted at a single center, the Norwegian Radium Hospital, Oslo. An open-label study design was employed in which lesions in patients fulfilling the inclusion criteria were identified and then randomized to treatment with one of the 3 concentrations of cream. Patients were either treated for 3 h or 18 h so that all lesions within any patient were treated with the same application time. The primary efficacy parameter was the distribution of PAP fluorescence in biopsies of verified nodular BCC lesions taken at the end of the period of application prior to photoactivation. Fluorescence of PAP across the full thickness of each lesion was measured using quantitative fluorescence microscopy with a highly light sensitive charge-coupled device camera, as exemplified in Figure 9 below. Despite the open study design, the pathologist performing microscopic fluorescence photometry was blinded to treatment.

Figure 9:         Measurement of Penetration Depth of MAL in Nodular BCC

 

 

 

 

 

 

 

 


Figure 9: Measurement of penetration depth of MAL in nodular BCC. MAL cream was applied to BCC lesions and histological section of the BCC was examined by fluorescence microscopy (left image) and regular HE staining (right image). The left panel is a black and white fluorescence image of a nodular BCC. Fluorescence appears as white. Right panel is the same section with HE staining to show the histological border of the BCC lesion.
In total, 18 patients with 32 verified nodular BCC lesions were treated, 5 or 6 lesions for each of the 6 dosage regimens. A further 11 lesions that were determined not to be nodular BCC were excluded from evaluation. It was intended that each lesion within a patient would be treated with a different concentration of MAL cream but to complete the study in a timely and balanced manner, 3 patients had more than 1 lesion treated with the same concentration.

Dose and Time-Dependency of Fluorescence in Nodular BCC

The concentration of methyl aminolevulinate in cream was positively associated with increased depth of penetration of PAP fluorescence (Figure 10, left panel). This was seen most consistently with the 3-h application time. The depths of fluorescence (mean + standard deviation, SD) were 0.7 + 0.4, 1.0 + 0.6, and 1.3 + 0.5 mm for the 16, 80, and 160 mg/g concentrations respectively. Depth of penetration was not increased with the longer (18‑h) application time and the concentration-response relationship was more variable (depth of penetration 0.5 + 0.4, 0.96 + 0.2 and 0.83 + 0.6 mm). In view of the greater depth of the lesions treated for 3 h, the relative depth of penetration (depth of fluorescence/depth of lesion) was also determined. Optimum penetration (98% + 4%; >90% in all lesions) was only achieved by the 160-mg/g concentration applied for 3 h (Figure 10, right panel).

Selectivity for Lesions

Selectivity was assessed by the pathologist who examined normal skin adjacent to the lesion for PAP fluorescence following application of MAL cream in accordance with the randomization schedule. Only 1 of 16 lesions treated with a 3-h application time was reported as showing ‘much’ fluorescence in normal skin. Fluorescence in normal skin was generally higher after an 18 h application time for all 3 cream strengths; 12 of 16 lesions were reported as showing ‘much’ fluorescence.

Figure 10:       Depth of PAP Fluorescence in Relation to MAL Cream Concentration and Application Time

 

 

 

 

 

 

 

 

 

 

 

 



5.3.3       Study 206/98

A Pharmacokinetic Study of Protoporphyrin IX formation in Patients with Actinic Keratosis and Basal Cell Carcinoma after Topical Application of P-1202 (MAL) Cream.

Objectives, Design, and Methods

The primary objective of Study 206/98 was to compare the fluorescence of PAP in superficial BCC and AK at different time intervals after topical application of methyl aminolevulinate cream containing concentrations of 0 mg/g (placebo, AK only), 16 mg/g, 80 mg/g, or 168 mg/g methyl aminolevulinate. Secondary objectives were to determine other pharmacokinetic parameters, response rate, and safety. In addition, PAP fluorescence was measured in normal skin and in treated normal skin.

This was a prospective, double-blind, randomized, controlled study performed at a single center. Seven consenting adult patients with at least 3 superficial BCC lesions and 8 patients with a minimum of 4 moderately thick AK lesions were recruited. The 3 BCC lesions per patient were randomized to be treated with one of the 3 treatments so that each patient received each treatment on a different lesion:

·         Methyl aminolevulinate 16 mg/g Cream for 28 hours,

·         Methyl aminolevulinate 80 mg/g Cream for 28 hours,

·         Methyl aminolevulinate 168 mg/g Cream for 28 hours.

The 4 AK lesions per patient were randomized for treatment with 1 of the 3 cream strengths or placebo.

The lesions were prepared before the application of the cream so that penetration of cream to the lesion would not be compromised. To standardize the preparation procedures, a guideline was provided, which described how crusts were to be removed by a small curette and that the surface was to be scraped gently in order to roughen the surface. This procedure is identical to that used in the Phase III trials.

After 28 hours, the dressing and excess cream were removed and lesions were illuminated with non-coherent light (570 to 670 nm) with a fluence of 75 J/cm2. Fluorescence in lesions and surrounding skin was measured with optical fiber point monitoring before cream application, subsequently at frequent intervals for 28 h during cream application, 1 h after illumination (at 29 h) and at 48 h.

Dose and Time-Dependency of Fluorescence in Lesions

Table 18 shows fluorescence measurements in the AK lesion at various times after cream application. Fluorescence measurements 1 hour after application were similar to those prior to application (data not shown). At 3 hours there was a clear increase in PAP fluorescence intensity in the lesions compared with levels at 1 hour or those with placebo. After log transformation of the data, the 95% CIs for the difference between fluorescence compared with placebo showed a statistically significant increase at 3 hours and 5 hours for the highest concentration (168 mg/g) cream. A significant increase in fluorescence was not shown for 16 mg/g and 80 mg/g applied for 3 and 5 hours. The 1‑hour application was not sufficient to show significance for any of the 3 methyl aminolevulinate cream concentrations.

 

Table 18:        PAP Fluorescence in Treated AK Lesions by Cream Concentration and Time of Measurement (Study 206/98)

 

Concentration of methyl aminolevulinate cream

Number of Lesions

PAP Fluorescence in Lesion

Mean ± SD

 

 

 

1 hour

3 hours

5 hours

21 hours

 

0 mg/g

8

30.3 ± 5.7

26.7 ± 5.1

26.3 ± 5.4

24.2 ± 3.5

 

16 mg/g

8

37.9 ± 9.9

59.9 ± 47.0

78.1 ± 77.0

92.0 ± 59.0

 

80 mg/g

8

37.5 ± 15.8

56.8 ± 36.6

68.1 ± 55.5

116.8 ± 95.1

 

168 mg/g

8

38.1 ± 12.3

61.4 ± 28.4

78.2 ± 42.8

113.1± 60.5

 

 

Data source: Table 7A in 206/98 study report.

Plots of median PAP fluorescence versus time in AK lesions showed dose-related increases from 3 hours onward, reaching a plateau at about 9 hours for the higher concentrations (data not shown). Although the results showed variation and mean results failed to show a significant dose-response relationship, higher doses generally achieved greater concentrations of PAP in lesions. Furthermore, only the PAP fluorescence intensity after the 168-mg/g strength was significantly different from that after placebo at 3 hours and 5 hours. The optimum duration of application of methyl aminolevulinate cream