Recently, the FDA cited its loss of confidence over the notoriously toxic P13K inhibitor drug class for blood cancers. The reason behind this is the concerning patient survival data across multiple clinical trials.
Stringent for P13K inhibitor drug class
Currently, the FDA aims to put the P13K inhibitor drug class under a severe stringent regulatory scope. During a briefing document ahead of an advisory committee meeting scheduled recently, the FDA stated that 6 randomized clinical trials have shown a trend that suggests 4 marketed PI3K inhibitors might shorten blood cancer patients’ life expectancy because of their toxicity.
The agency added: “The unprecedented observation raises a red flag for PI3K inhibitor approvals based on single-arm trials. In those studies, drug reviewers cannot properly evaluate the life-extension marker known as overall survival. Therefore, the agency says future PI3K nods should use randomized clinical trials with active comparators.”
According to Richard Pazdur, M.D., Director of the FDA’s Oncology Center of Excellence, single-arm trials do not allow to take a look at toxicity (because) one does not have a comparator there, and this is particularly a problem in indolent diseases that people may live for prolonged years.
P13K Inhibitor Approvals
In its review document, the FDA’s oncology team noted that the P13K inhibitor drug class developers in question did not do a good enough job exploring lower doses of their products, which could potentially reduce toxicities.
Although the FDA seems to have made up its mind, it’s now asking external experts to weigh in on whether future PI3K inhibitor approvals in blood cancers should strictly use overall survival from randomized trials. Before the public meeting, the FDA has already successfully dissuaded Incyte from pursuing a nod of its PI3K delta inhibitor parsaclisib in certain indolent non-Hodgkin lymphomas based on single-arm data.
Patient survival is both an efficacy and safety marker, the FDA says. And for these PI3K inhibitors, which have shown favorable effects on anti-tumor efficacy but not eventually on prolonging life, “substantial toxicity” could have tipped the benefit-risk balance against the drugs.
The FDA has approved four PI3K inhibitors for various blood cancers: Gilead Sciences’ Zydelig, Bayer’s Aliqopa, Secura Bio’s Copiktra and TG Therapeutics’ Ukoniq. Novartis’ Piqray, a PI3K alpha-specific inhibitor approved for breast cancer, is not part of the group under FDA scrutiny thanks to its different mechanism of action.