What happened

Shares of Endocyte (NASDAQ:ECYT) closed up 11.4% on Monday after the company disclosed that the U.S. Food and Drug Administration will allow it to use radiographic progression-free survival (rPFS) as an endpoint in its clinical trial -- the Vision study -- being conducted to support the approval of 177Lu-PSMA-617 for the treatment of metastatic castration-resistant prostate cancer.

So what

rPFS measures the time it takes for a tumor to start growing again as determined by X-rays or for the patient to die (whichever comes first). Since most patients will trigger the rPFS event through progression of their disease rather than death, measuring rPFS is faster than measuring overall survival.

Endocyte had previously expected to conduct two interim assessments of overall survival after 50% and 70% of the events had occurred, but will now make one efficacy analysis after 450 rPFS events. The analysis of rPFS is expected to occur before the end of 2019, while the overall survival analysis, which Endocyte still plans to do, will occur near the end of 2020.

Doctor and patient sitting at a table

Image source: Getty Images.

Now what

The switch from overall survival to rPFS is obviously good for Endocyte because it could allow 177Lu-PSMA-617 to get on the market in the U.S. faster. There's also the possibility of getting the same endorsement of rPFS from European regulators who will consider the idea shortly.

Seeing an opportunity to take advantage of its higher share price, Endocyte announced after the closing bell that it plans to sell $175 million of stock. Naturally, shares are down after hours because of the dilution the secondary offering will cause.

We'll have to see where Endocyte will price its secondary offering, but wherever shares end up, the long-term valuation will be determined by whether the Vision study is positive and Endocyte can get 177Lu-PSMA-617 approved.

Brian Orelli and The Motley Fool have no position in any of the stocks mentioned. The Motley Fool has a disclosure policy.