FDA Rejects Approval of Oral Paclitaxel Plus Encequidar for Metastatic Breast Cancer: Here’s Why

Last week, the Food and Drug Administration (FDA) was scheduled to make a decision on whether or not they would approve oral paclitaxel plus encequidar for the treatment of metastatic breast cancer. The agency decided not to approve the regimen, and issued a complete response letter outlining why.

In the letter, the FDA expressed concern about increased neutropenia-related sequelae in patients given oral paclitaxel plus encequidar compared to the IV paclitaxel arm in the phase 3 KX-ORAX-001 clinical trial.

Additionally, there was uncertainty regarding overall response rates (ORR) at week 19. The ORR was reviewed by a blinded independent central review, whose reconciliation and re-read process may have led to unmeasured bias and influence.

“Our clinical and regulatory teams are disappointed by the complete response letter,” said Dr. Rudolf Kwan, Chief Medical Officer of Athenex, the manufacturer of the agent. “We plan to work with the Agency to resolve the issues raised in the CRL and to obtain approval for oral paclitaxel plus encequidar in metastatic breast cancer.”

The FDA recommends that a new clinical trial be conducted evaluating oral paclitaxel plus encequidar in a representative sample of patients with metastatic breast cancer. This trial should include strategies to improve side effects, such as dose optimization and/or exclusion of patients who are at higher risk of toxicities.

“We remain committed to the breast cancer community and will explore the best path forward to obtain regulatory approval. In the interim, we will identify and undertake the appropriate internal organizational adjustments accordingly,” said Dr. Johnson Lau, Chief Executive Officer of Athenex.

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