What happened

After unveiling positive results for its lead drug, sacituzumab govitecan, in breast cancer at the influential American Society of Clinical Oncology (ASCO) conference, shares in Immunomedics (NASDAQ:IMMU) rallied by as much as 14.7% today before settling in for a gain of 9.3% at 3 p.m. EDT.

So what

Sacituzumab govitecan is an anti-TROP-2 antibody that may have activity in multiple tumor types, including breast cancer, lung cancer, and colorectal cancer that overexpress the TROP-2 protein.

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At ASCO 2018, data was updated for the use of sacituzumab govitecan in advanced-stage estrogen receptor-positive (ER+)/human epidermal growth factor receptor 2-negative (HER2–) metastatic breast cancer, a patient group with limited treatment choices.

The data include a 31% overall response rate (ORR), a median duration of response of 7.4 months, and median progression-free survival of 6.8 months. Those results were particularly solid given that these patients were heavily pretreated, with each having already received a median of five prior lines of treatment.

Now what

Management is going to discuss the data with regulators to figure out how quickly it can get sacituzumab govitecan a Food and Drug Administration review. The FDA could offer an accelerated pathway, or it could require additional phase 3 testing. Historically, response rates following one line of chemotherapy are between 10% to 20%, so it appears Immunomedics' data matches up well to existing treatment choices.

Also helping its chances is the fact that sacituzumab govitecan has already been submitted for an FDA approval for use as a third-line treatment in triple negative breast cancer patients after delivering a 31% ORR in that patient group in phase 2 studies.

Given there's a big need for new treatment options in late-stage breast cancer patients, Immunomedics could have a nine-figure commercial drug on the market in less than a year, if regulators cooperate.