Odonate Therapeutics is ending development of its oral chemotherapy drug and closing up shop after the FDA deemed the drug’s clinical data “unlikely to support FDA approval.” As it winds down its operations, the company will work with clinical sites to switch patients participating in its clinical trials to alternative treatments, the company said in a statement Monday.
Odonate had been developing the drug, tesetaxel, for the treatment of metastatic breast cancer. It is a taxane, the same drug class as paclitaxel and docetaxel, but, unlike its peers, it is given orally, not intravenously.
Tesetaxel was in multiple phase 2 studies testing it alone and in combination with other medicines, including the chemo drug capecitabine in HER2-negative breast cancer and checkpoint inhibitors in triple-negative breast cancer.
In its phase 3 study, the company pitted tesetaxel and capecitabine against capecitabine alone in 685 patients with HR-positive, HER2-negative metastatic breast cancer. The combination treatment staved off cancer progression for a median of 9.8 months versus 6.9 months for capecitabine alone, top-line data from August 2020 show.
Although the study was technically a success, having met its primary endpoint, the 2.9-month difference in progression-free survival was disappointing. Its shares dropped 35% in early trading the day it revealed those results. The company plugged on with its work, dosing a new patient group in a phase 2 study as recently as December 2020.
“Expectations were for around a 3.5 month benefit, so the efficacy result was on the low side for many, and this modest improvement also came with side effects,” Evaluate wrote at the time.
Those side effects included severe neutropenia, or a low white blood cell count, which affected nearly three-quarters of patients taking tesetaxel and capecitabine, but 8% of those taking capecitabine alone. This echoed data seen when tesetaxel was in different hands: It was placed on hold in 2006 when Daiichi Sankyo was developing it due to patient deaths from severe neutropenia.