What happened

Shares of the clinical-stage biotech Five Prime Therapeutics (NASDAQ:FPRX) are up by a jaw-dropping 364% in pre-market trading Wednesday morning. The biotech's stock is popping in response to positive midstage trial results for the stomach cancer drug candidate bemarituzumab.

Specifically, Five Prime and partner Zai Lab (NASDAQ:ZLAB) reported that the combination of bemarituzumab and mFOLFOX6 chemotherapy beat out placebo plus mFOLFOX6 on three efficacy endpoints -- median progression-free survival, median overall survival, and overall response rate -- in patients with fibroblast growth factor receptor 2b-positive, HER2-negative front-line advanced gastric or gastroesophageal junction cancer. Zai Lab owns the drug's developmental and commercial rights within China through a licensing deal with Five Prime.  

A businessman throwing money into the air.

Image source: Getty Images.

So what

Bemarituzumab will likely still have to pass muster in a larger pivotal stage trial to gain approval in either China or the United States. But a first-line stomach cancer drug unquestionably sports an enormous commercial potential. Stomach cancer, after all, is one of the most common types of malignancies, as well as a leading cause of death across the globe. With this background in mind, it's not surprising see investors pouring into this small-cap biotech stock this morning.  

Now what

Five Prime and Zai Lab, per yesterday's press release, also noted that bemarituzumab may sport anti-cancer activity across a range of solid tumors, such as squamous non-small cell lung cancer, triple negative breast cancer, ovarian cancer, pancreatic cancer, and intrahepatic cholangiocarcinoma.

What this means is that bemarituzumab might turn out to be a franchise-level cancer medicine. As such rare gems rarely go unnoticed by big pharma, Five Prime will probably bubble to the top of the buyout rumor mill soon. Stay tuned. 

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