Pfizer has started a Phase III trial assessing orphan drug rivipansel as a treatment for sickle cell disease patients hospitalised with vaso-occlusive crisis, a common and very painful complication of the condition.

Vaso-occlusive crisis - which occurs when blood vessels become clogged by sickled red blood cells, leading to ischaemic injuries and potentially organ damage - causes more than 75,000 hospitalisations every year.

Pfizer’s Phase III trial aims to assess the safety and efficacy of rivipansel (GMI-1070), the primary endpoint being time to readiness-for-discharge and key secondary endpoints including time to discharge, cumulative IV opioid consumption and time to discontinuation of IV opioids.

Rivipansel is an investigational pan-selectin inhibitor, thought to play a key role in regulating cellular interactions within blood vessels, which Pfizer picked up through a worldwide development and commercialisation license agreement with GlycoMimetics in 2011.

The start of this trial has triggered a $20-million milestone to GlycoMimetics, adding to a $15-million payment received last year.