What happened

Shares of Endocyte (NASDAQ:ECYT) are up 7.5% as of 12:11 p.m. EDT, having been up as much as 18% today, after the biotech released updated data from its phase 2 trial testing 177Lu-PSMA-617. It will be presented at the American Society of Clinical Oncology (ASCO) annual meeting next month.

So what

In 50 late-stage prostate cancer patients, 177Lu-PSMA-617 produced a 50% reduction in the level of prostate-specific antigen (PSA) in 62% of patients, while 44% of patients had a PSA reduction of 80% or greater. The data is a slight improvement from the first 30 patients, in which 57% of patients reached the 50% threshold and 43% reached the 80% threshold. PSA is a marker of prostate cells, so the assumption is that the reduction in PSA levels is caused by a reduction in the tumor volume.

Doctor talking to patient at a table

Image source: Getty Images.

While PSA is an OK marker, what doctors and their patients really care about is survival. Unfortunately -- or fortunately, depending on how you look at it -- the median overall survival data isn't available yet. It's fortunate because the last 20 patients enrolled in the trial had only been followed for six to nine months when the data was submitted for the ASCO abstract, so we know they've lived a median of at least that long. Endocyte previously reported that the first 30 patients in the trial had a median overall survival of 13.5 months.

Now what

There isn't much for investors to do at this point but wait. The poster, which should have updated data from the 50 patients, is scheduled to be presented on June 2. And on the evening of June 4, the company will present a webcast of the data.

No matter how the data turns out, Endocyte has committed to testing 177Lu-PSMA-617 in a phase 3 trial, which is scheduled to enroll the first patient this quarter.

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