What happened

After the company unveiled the design of its phase 3 trial for GMI-1271 in relapsed or refractory acute myeloid leukemia (AML), GlycoMimetics (NASDAQ:GLYC) shares fell 19.2% as of 1 p.m. EST.

So what

In December, management unveiled updated results from a trial evaluating GMI-1271 in AML patients, which sparked hope that the drug could quickly become part of standard care alongside chemotherapy. Specifically, the clinical remission rate for GMI-1271 patients was 43% at a median follow-up of 6.6 months, and median overall survival was 9.4 months. That compared nicely to the median overall survival of up to 5.4 months for a matched control group of patients receiving only chemotherapy.

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While the overall survival data is compelling, investors had hoped that GlycoMimetics might choose a surrogate endpoint for its phase 3 trial that could allow for faster data collection, and thus a quicker review timeline by the Food and Drug Administration. Those hopes were dashed after the closing bell on Monday, when management revealed that it will indeed use overall survival as its primary endpoint.

Now what

The decision to wait for overall survival data could push back a filing for FDA approval by six to nine months. That will undeniably set back any timeline to profitability for the company.

Nevertheless, investors could be overreacting to this news. Overall survival is the gold standard; if GMI-1271 successfully extends it, then it will gain an important advantage over other therapies that have won an OK in the indication based on surrogate endpoints, such as overall response rate.

Therefore, this appears to be a smart long-term decision that may eventually more than make up for any short-term sales delay, especially because adding GMI-1271 could make chemotherapy safer. Typically, toxicity to chemotherapy increases when you add drugs, but in GMI-1271's trials so far, that hasn't been the case. For example, severe mucositis usually occurs in 20% to 25% of patients treated with MEC (mitoxantrone, etoposide, and cytarabine), but it only occurred in about 4% of patients given MEC plus GMI-1271.

Of course, there's no guarantee GMI-1271's phase 3 trial pans out, and unfortunately, data from the trial won't be available until 2020. This means investors are going to have to be patient. But in the meantime, investors will get data later this year from Pfizer's trial of rivipansel, a sickle-cell disease drug it licensed from GlycoMimetics, and in 2019, there should be data from an early stage trial of GMI-1271 in multiple myeloma.

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.