Pfizer has acknowledged that the synthetic glycomimetic it licensed from GlycoMimetics in 2011 has failed a Phase III trial in patients with sickle cell disease (SCD) who were hospitalized for a vaso-occlusive crisis (VOC) and required treatment with intravenous (IV) opioids—a clinical setback that sent GlycoMetics shares plunging by more than half their value in morning trading.

Rivipansel missed its primary endpoint in the Phase III Evaluating Safety, Efficacy and Time to Discharge (RESET) pivotal study (NCT02187003) of time to readiness-for-discharge. The drug candidate also missed the trial’s key secondary endpoints of time-to-discharge, cumulative IV opioid consumption, and time to discontinuation of IV opioids, Pfizer said.

“We are disappointed with the results, as we have been working in close partnership with the SCD community to advance rivipansel as a potential treatment option for acute VOC,” Brenda Cooperstone, MD, SVP, and chief development officer, rare disease, Pfizer Global Product Development, said in a statement issued Friday evening.

Pfizer did not release data from the trial. Cooperstone said that data would be shared at an unspecified upcoming scientific meeting, “as we want to ensure the learnings from this trial help inform future sickle cell programs that aim to improve care for SCD patients experiencing a VOC.”

Investors responded to the Phase III failure with a stock selloff that sent GlycoMimetics shares falling 56% from Friday’s close of $9.13 a share in pre-market trading today, to $3.98 a share as of 9:15 a.m.

Rivipansel is a synthetic glycomimetic designed to act as a pan-selectin antagonist, inhibiting all three selectin types which are implicated in inflammatory processes: E-selectin, L-selectin, and P-selectin.

Up to $340M collaboration

Pfizer licensed Rivipansel—then called GMI-1070—in October 2011, agreeing to pay GlycoMimetics up to $340 million in upfront and milestone payments, plus royalties. According to GlycoMimetics’ Form 10-K for 2018, Pfizer has paid GlycoMimetics $22.5 million upfront, and $35 million tied to the dosing of the first patient in RESET, consisting of a $15 million non-refundable payment in May 2014 and a $20 million payment in August 2015.

“There have been no additional payments received from Pfizer since 2015,” GlycoMimetics stated.

Pfizer had overseen RESET, having agreed to assume responsibility for clinical development of rivipansel since completion of a Phase II study, under terms of the licensing agreement.

RESET was a multicenter, randomized, double-blind, placebo-controlled, parallel-group study designed to evaluate the efficacy and safety of rivipansel in patients with SCD aged six and older, who were hospitalized for a VOC and required treatment with intravenous opioids.

The trial included 345 patients who were randomized 1:1 to receive rivipansel or placebo, administered intravenously every 12 hours to a maximum of 15 doses. All study participants were followed for safety for 35 days after their last dose of study drug.

“We are both surprised and deeply disappointed by this outcome, as we had strongly hoped that rivipansel would have a positive benefit for people living with sickle cell disease,” added GlycoMimetics CEO Rachel King.

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