The US Food and Drug Administration (FDA) on Wednesday finalized its guidance on developing topical drugs to treat head lice.
The US Centers for Disease Control and Prevention estimates that between six and 12 million Americans between the ages of 3 and 11 get head lice each year.
Despite there being a number of already-approved prescription and over-the-counter treatments for head lice in the US, FDA says it wants to encourage the development of new treatments in light of increasing resistance to commonly used treatments such as lindane and pyrethroids.
FDA says that drugmakers should identify the active components of the drug they wish to study early on, and, if they are developing a product with multiple active ingredients, they should talk to the agency about assessing the "contribution to efficacy of each of the active ingredients."
Because head lice mostly affect children, FDA says sponsors should also contact the agency early on to discuss designing appropriate studies in pediatric populations to get recommendations from the agency regarding dose selection and the size of the preapproval safety database.
FDA says it has historically waived pediatric study requirements for head lice treatments in patients less than six months old, and adds that sponsors may be able to get waivers for other reasons, listing two examples: "e.g., there was evidence of lack of meaningful therapeutic benefit over existing treatments and was not likely to be used by a substantial number of patients in that age group or there was strong evidence suggesting the drug is ineffective or unsafe in that age group."
FDA also says that clinical trials for head lice treatments "should be representative of the target population for which the drug is intended for use," and says that sponsors should also take geographical diversity into account as "resistance patterns to some drugs vary by location."
During clinical trials, FDA says sponsors should look out for both local and systemic safety issues, and monitor for known complications including neurotoxicity, neonatal toxicity and inhibition of acetylcholinesterase.
Additionally, FDA says that pharmacokinetic trials should be conducted under "maximal use conditions," meaning that the trial should include "an adequate number of subject at the upper end of severity of lice infestation," and use the "maximal dosing anticipated in both phase 3 trials."
Phase III Considerations
For Phase III clinical trials, FDA says sponsors can typically conduct two vehicle-controlled studies in order to demonstrate efficacy.
However, FDA says that sponsors may need to use an active control if studying drugs with clinically significant risks such as neurotoxicity in order to demonstrate that the drug has a meaningful benefit.
Additionally, FDA says sponsors submit the specifications of any devices, such as lice combs, that are used as part of the treatment regimen as early as possible.