FDA clears Takeda, Protagonist's first-in-class PV drug

Takeda and Protagonist Therapeutics' hepcidin mimetic rusfertide has been approved by the FDA to treat polycythaemia vera (PV), offering a new type of therapy for patients living with the rare blood disorder.

The first-in-class drug has been cleared under the Mimrylo brand name to treat erythrocytosis (overproduction of red blood cells) in adults with PV, a condition that leads to a thickening of the blood and an increased risk of blood clots that can cause serious cardiovascular problems, such as stroke and heart attack.

Like hepcidin itself, rusfertide is thought to regulate iron homeostasis and control the absorption, storage, and distribution of iron in the body, helping to control the body's production of red blood cells.

Takeda bought rights to rusfertide from Protagonist last year for $300 million upfront in a deal that could be worth up to $1.675 billion if the drug reaches regulatory and commercial objectives.

The approval is based on the phase 3 VERIFY trial, which showed that a once-weekly, self-administered dose of subcutaneous Mimrylo was associated with a clinical response in 77% of patients, compared to 33% of a matched placebo arm.

Patients in the study were dependent on routine blood draws (phlebotomy), a go-to treatment that aims to remove excess red blood cells until they reach normal levels, and a response was defined as no need for a phlebotomy procedure during weeks 20 to 32 after treatment started.

The drug also showed sustained control of haematocrit – the percentage of total blood volume that is made up of red blood cells – over 52 weeks, with the average level staying below the target of 45%.

PV affects around 90,000 people in the US, with a similar number in Europe. At the moment, drug treatments approved by the FDA for PV also include hydroxyurea or interferons, which are not particularly effective at controlling blood counts and can be poorly tolerated, as well as Novartis' JAK 1/2 inhibitor Jakafi/Jakavi (ruxolitinib) as a second-line option for refractory patients.

"People living with PV often experience complex and invisible symptoms, from extreme fatigue to the emotional strain of living with a chronic blood cancer," said Kapila Viges, chief executive of the MPN Research Foundation, which advocates for people living with myeloproliferative neoplasms like PV.

"At the same time, we know that every patient's experience with PV is different, underscoring the need to continue to listen closely to the community to understand what matters most," he added. "This meaningful approval reflects important progress and brings forward a new treatment option in a disease where patients have long needed innovation and more choices."

According to a Reuters report, Mimrylo is being made available straight away and will cost about $4,200 per vial, or around $218,000 per year. Analysts at Jefferies have predicted that annual sales could eventually reach around $2 billion.