Immunomedics’ (NASDAQ:IMMU) Phase I/II sacituzumab govitecan hormone receptor positive (HR+) Her2-negative breast cancer data may not be enough for an accelerated approval despite showing clinically significant responses in a heavily pretreated population and a similar path adopted in triple-negative breast cancer (TNBC), experts said.
On the sidelines of the ASCO meeting last week, the company’s chief business officer, Usama Malik, said that due to the compelling activity seen in Phase I/II (NCT01631552) data, the company will consider their registrational approach in HR+ Her2-negative after discussions with key opinion leaders and regulatory authorities. Immunomedics is considering a number of options like using the Phase I/II data to support a filing or converting the single-arm study to a randomized one, said Malik, but did not comment on specific timelines.
Analysts thought the Phase I/II data established proof-of-concept, and they compared sacituzumab to other CDK4/6 inhibitors like Eli Lilly’s (NYSE:LLY) Verzenio (abemaciclib) -- whose initial approval was based on a single-arm study -- and suggested a similar path for approval. One analyst said the overall response rate (ORR) and median duration of response is in line with data used to file for an accelerated approval in metastatic TNBC (mTNBC), while others expect the Phase II data to support a breakthrough designation and potential fast-to-market path for that indication.
However, experts told this news service that while impressive in a heavily pretreated population, the data would unlikely be adequate for an accelerated approval. They said a direct randomized comparison with a chemotherapy like Roche’s (VTX:ROG) Xeloda (capecitabine) was required to provide further evidence of efficacy, since the HR+ Her2-negative breast cancer space has more options and a higher expectation of efficacy than TNBC.