FDA Finalizes Photosafety Testing Guidance

The FDA emphasized flexibility in a final guidance that attempts to harmonize U.S. and International Conference on Harmonisation drug photosafety testing requirements.

If the compound in question is poorly soluble, for example, drugmakers may not find it appropriate to conduct an in vitro assay and may choose an animal or human assessment.

If the in vitro test is positive, drugmakers could consider conducting a phototoxicity study in animals to see if the same results come up in vivo — unless existing use information can support a case for low risk of phototoxicity.

If a positive in vivo result can’t be mitigated using a risk assessment, then the FDA recommends conducting a clinical study. A negative in vivo result would be sufficient evidence that the product is not directly phototoxic and no further testing is necessary.

In all cases, a clinical phototoxicity assessment indicating no concern supersedes positive nonclinical results, the guidance says.  

The FDA removed the section on drugs delivered via the eye, as the ICH S10 guideline doesn’t offer concrete recommendations in this area.

View S10 Photosafety Evaluation of Pharmaceuticals at www.fdanews.com/01-26-15-photosafetyguidance.pdf. — Lena Freund