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 surgery^27,[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 CureLight^TM 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

 

 

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]).