Vandetanib-induced phototoxicity in human keratinocytes NCTC-2544

Cellular photo(geno)toxicity of gefitinib after biotransformation

Gefitinib (GFT) is a selective epidermal growth factor receptor (EGFR) inhibitor clinically used for the treatment of patients with non-small cell lung cancer. Bioactivation by mainly Phase I hepatic metabolism leads to chemically reactive metabolites such as O-Demethyl gefitinib (DMT-GFT), 4-Defluoro-4-hydroxy gefitinib (DF-GFT), and O-Demorpholinopropyl gefitinib (DMOR-GFT), which display an enhanced UV-light absorption. In this context, the aim of the present study is to investigate the capability of gefitinib metabolites to induce photosensitivity disorders and to elucidate the involved mechanisms. According to the neutral red uptake (NRU) phototoxicity test, only DF-GFT metabolite can be considered non-phototoxic to cells with a photoirritation factor (PIF) close to 1. Moreover, DMOR-GFT is markedly more phototoxic than the parent drug (PIF = 48), whereas DMT-GFT is much less phototoxic (PIF = 7). Using the thiobarbituric acid reactive substances (TBARS) method as an indicator of lipid photoperoxidation, only DMOR-GFT has demonstrated the ability to photosensitize this process, resulting in a significant amount of TBARS (similar to ketoprofen, which was used as the positive control). Protein photooxidation monitored by 2,4-dinitrophenylhydrazine (DNPH) derivatization method is mainly mediated by GFT and, to a lesser extent, by DMOR-GFT; in contrast, protein oxidation associated with DMT-GFT is nearly negligible. Interestingly, the damage to cellular DNA as revealed by the comet assay, indicates that DMT-GFT has the highest photogenotoxic potential; moreover, the DNA damage induced by this metabolite is hardly repaired by the cells after a time recovery of 18 h. This could ultimately result in mutagenic and carcinogenic effects. These results could aid oncologists when prescribing TKIs to cancer patients and, thus, establish the conditions of use and recommend photoprotection guidelines.

Phototoxic Reaction Induced by Pazopanib

Multikinase inhibitors (MKIs) are a novel target therapy that offers promising long-term survival for patients with advanced-stage cancer. However, they cause a wide range of adverse reactions, skin and skin appendage being the most prevalent. Photosensitivity reactions are well-recognized effects from certain MKIs such as sunitinib and vandetanib. However, phototoxic reaction induced by pazopanib has never been reported. We present here the first case of pazopanib-induced phototoxic drug reaction in a patient with renal cell carcinoma.

Identification and characterization of in vivo, in vitro and reactive metabolites of vandetanib using LC-ESI-MS/MS

Vandetanib (Caprelsa tablets, VNT) is an orally inhibitor of vascular endothelial growth factor receptor 2. The current research reports the characterization and identification of in vitro, in vivo and reactive intermediates of VNT. In vitro metabolites of VNT were performed by incubation with rat liver microsomes (RLMs). Extraction of vandetanib and its in vitro metabolites from the incubation mixtures were done by protein precipitation. In vivo metabolism was done by giving one oral dose of vandetanib (30.8 mg/kg) to Sprague Dawley rats in metabolic cages by using oral gavage. Urine was gathered then filtered at certain time intervals (0, 6, 12, 18, 24, 48, 72, 96 and 120 h) from vandetanib dosing. A similar volume of ACN was added to each collected urine sample. Both layers (organic and aqueous) were injected into liquid chromatography electro spray ionization tandem mass spectrometry (LC-ESI-MS/MS) to detect in vivo vandetanib metabolites. N-methyl piperidine ring of vandetanib is considered a cyclic tertiary amine that undergoes metabolism forming iminium intermediates that are very reactive toward nucleophilic macromolecules. Incubation of vandetanib with RLMs in the presence of 1.0 mM KCN was made to check reactive metabolites as it is usually responsible for noticeable idiosyncratic toxicities including phototoxicity and QT interval prolongation. Four in vivo phase I, one in vivo phase II metabolites, six in vitro phase I metabolites and four cyano conjugates of vandetanib were detected by LC-MS/MS. In vitro and in vivo phase I metabolic reactions were N-oxide formation, N-demethylation, α-carbonyl formation and α-hydroxylation. In vivo phase II metabolic reaction was direct conjugation of vandetanib with glucuronic acid. All metabolic reactions occurred in N-methyl piperidine of vandetanib which causes toxicity and instability of vandetanib.

Development of Photoonycholysis with Vandetanib Therapy

Vandetanib therapy is a novel once-daily oral multitargeted tyrosine kinase inhibitor, which is currently used in advanced or metastatic medullary thyroid cancer. Skin toxicities are among the most prevalent adverse events reported with this targeted therapy (e.g. acne-like rash, hand-foot skin reaction, hair changes, and paronychia). In addition, photosensitivity reactions may affect more than one third of treated patients. We report here 2 patients developing photosensitivity reactions with vandetanib therapy, including photoonycholysis. Our patients presented a wide range of phototoxic reactions with exaggerated sunburn reactions solely located to photoexposed areas or hyperpigmentation with visible blue dots. More importantly, both patients concomitantly developed nail changes consistent with type 1 photoonycholysis, which had never been reported so far neither with vandetanib therapy nor with other anticancer-targeted therapies. In addition, histopathologic findings and reflectance confocal microscopy imaging performed in one patient suffering from photodistributed skin hyperpigmentation both strengthen the likelihood of a postinflammatory mechanism. Clinicians should be aware of these underestimated but very characteristic photoinduced adverse events, which can lead to treatment interruption and require very strict photoprotective measures in treated patients.

A molecular insight into the phototoxic reactions observed with vemurafenib, a first-line drug against metastatic melanoma

The electronic properties of vemurafenib (VB) provide a rational basis for understanding its strong UVA-induced phototoxicity. Thus, solvation of hydrophobic VB by hydrogen bonding solvents controls its photophysical, photochemical and photosensitizing properties. Addition of phosphate buffered saline (PBS) to methanol (MeOH) induces a bathochromic shift of the VB absorbance spectrum and a fluorescence emission (λmax = 450 nm, quantum yield (Φ) = 0.011). Phosphorescence (λmax = 461 nm) is observed at 77 K in MeOH. 308 nm laser flash spectroscopy demonstrates that the lifetimes (τ) and quantum yields of the VB triplet state ((3)T(*)(1)) in deaerated MeOH (τMeOH = 0.41 μs, λmax ∼ 380 nm), MeOH-PBS and HSA solutions markedly depend on the microenvironment. A long-lived radical (half-life >200 μs) is also formed. The state (3)T(*)(1) is quenched by O2 and electron donors (Cys and 2'-deoxyguanosine) at a rate constant >1 × 10(9) M(-1) s(-1). UVA-irradiation of VB in air-saturated MeOH or MeOH-PBS solutions produces a UVA-absorbing photoproduct (Φ ∼ 5 × 10(-4)). VB photosensitizes Trp destruction by type I (radical formation) and type II (singlet oxygen ((1)O2) formation) photodynamic reactions (Φ = 0.005). Singlet oxygen production is further demonstrated by the VB-photosensitized His oxidation (ΦMeOH = 0.006).