Vemurafenib skin phototoxicity is indirectly linked to ultraviolet A minimal erythema dose decrease

• Published in: British journal of dermatology (1951) Vol. 171; no. 6; pp. 1529 - 1532
• Main Authors: Brugière, C., Stefan, A., Morice, C., Cornet, E., Moreau, A., Allouche, S., Verneuil, L.
• Format: Journal Article
• Language: English
• Published: Oxford Blackwell Publishing Ltd 01.12.2014; Wiley-Blackwell
• Subjects: Adult; Aged; Antineoplastic Agents - adverse effects; Biological and medical sciences; Dermatitis, Phototoxic - etiology; Dermatology; Dose-Response Relationship, Radiation; Erythema - etiology; Female; Humans; Indoles - adverse effects; Male; Medical sciences; Melanoma - drug therapy; Middle Aged; Prospective Studies; Skin involvement in other diseases. Miscellaneous. General aspects; Skin Neoplasms - drug therapy; Sulfonamides - adverse effects; Ultraviolet Rays - adverse effects; Photosensitivity; Skin disease; UVA radiation; Decrease; Minimal erythema dose; Dermatology; Toxicity; Phototoxicity; Skin
• ISSN: 0007-0963; 1365-2133; 1365-2133
• DOI: 10.1111/bjd.13300

Summary Background Vemurafenib, an anti‐rapidly accelerated fibrosarcoma kinase B (BRAF) molecule, improves survival among patients with metastatic BRAF‐mutated melanoma. Photosensitivity, a frequent cutaneous adverse effect induced by vemurafenib, can lead to cessation of treatment. Objectives To investigate photosensitivity mechanisms in patients treated with vemurafenib for metastatic melanoma. Methods In a prospective study of 12 patients, photobiological explorations with measurements of ultraviolet A (UVA) minimal erythema dose (MED) and polychromatic MED were performed over 3 days in all 12 patients. UVA MED and polychromatic MED were also assessed for four patients before treatment. We then performed spectrophotometric analyses of (i) serum and faeces in these four patients, before and after introduction of vemurafenib; (ii) the lyophilized form of vemurafenib without excipient added; and (iii) the lyophilized form of vemurafenib added to serum and faeces before treatment. Results Photosensitivity was present in 92% of the patients. UVA MED was normal before treatment and decreased after treatment, while polychromatic MED remained normal. The same three peaks (210, 260 and 310 nm) were identified in the spectrum for UVB and UVC but not for UVA on spectrophotometric analyses for each condition (lyophilized vemurafenib; serum and faeces after introduction of vemurafenib; and lyophilized vemurafenib added to serum and faeces before treatment). The peaks were different before treatment. Conclusions Our study confirms that photosensitivity under vemurafenib treatment was a UVA phototoxicity reaction, and our results suggest that a metabolite of vemurafenib rather than the parent molecule is involved in this phototoxicity. What's already known about this topic? Photosensitivity under vemurafenib is a phototoxicity reaction linked to ultraviolet A (UVA) radiation. What does this study add? We confirm photosensitivity linked to UVA radiation. We address the question of the spectrum of vemurafenib using spectrophotometric analyses of lyophilized vemurafenib, and of patient serum and faeces before and after the introduction of vemurafenib. We show peaks in UVB and UVC, but not in UVA, suggesting that UVA phototoxicity is linked to a metabolite rather than to the parent molecule.