Opna Bio has received the US Food and Drug Administration’s (FDA) orphan drug designation for OPN-2853 (zavabresib), a bromodomain and extra-terminal motif (BET) small molecule inhibitor, to treat myelofibrosis.

The International Nonproprietary Names (INN) approved the generic name zavabresib for OPN-2853.

Myelofibrosis is a rare blood cancer involving bone marrow scarring, resulting in anaemia, severe fatigue, ineffective production of blood cells, and an enlarged spleen. This disease affects 25,000 people in the US.

The designation applies to investigational therapies that target rare diseases affecting less than 200,000 people in the US. Benefits include waiver of certain FDA fees, eligibility for seven years of market exclusivity upon approval, and tax credits on clinical trial costs.

In the ongoing Phase I PROMise study, which is led by Professor Adam Mead at the University of Oxford in partnership with Cancer Research UK, zavabresib is being studied as an add-on to ruxolitinib to treat patients with myelofibrosis who no longer respond to ruxolitinib.

Opna Bio’s pipeline includes OPN-6602, in Phase I trials for multiple myeloma; OPN-2853, in a combination Phase I study with ruxolitinib for myelofibrosis.

Opna Bio CEO Reinaldo Diaz said: “Receiving orphan drug designation for zavabresib in myelofibrosis is a significant regulatory milestone for Opna Bio and highlights the urgent need for new and effective treatment options for patients with this disease.

“Our investigator-sponsored clinical trial with zavabresib and ruxolitinib has shown impressive results to date, including durable spleen reduction in patients with advanced myelofibrosis.

“We believe that selective BET inhibition alongside JAK inhibition offers a promising new therapeutic approach for patients with myelofibrosis. We are further encouraged by recent positive meetings with the FDA to continue to test zavabresib in additional clinical studies.”