CTI BioPharma clinches long-awaited FDA approval for myelofibrosis blockbuster prospect Vonjo

It’s been a long and tortuous path to approval for CTI BioPharma’s JAK2 inhibitor pacritinib, but the Seattle-based drugmaker’s cancer med has finally crossed the FDA finish line. The green light, which could unlock blockbuster sales at peak, sent CTI’s stock skyrocketing by more than 50% Tuesday morning.

The FDA on Monday signed off on CTI’s pacritinib, now christened Vonjo, to treat adults with intermediate- or high-risk primary or secondary myelofibrosis with a platelet count below 50 × 10^9/L. Vonjo boasts the distinction of being the first approved therapy to specifically address the needs of patients with cytopenic myelofibrosis, CTI said in a release.

"In the U.S., there are approximately 21,000 patients with myelofibrosis, two-thirds of which have cytopenias (thrombocytopenia or anemia), commonly resulting from the toxicity of other approved therapies,” Adam Craig, M.D., Ph.D., president and CEO at CTI, said in a statement.

“Severe thrombocytopenia, defined as a blood platelet count below 50 × 10^9/L, occurs in one-third of the overall myelofibrosis population, and has a particularly poor prognosis,” the CEO explained.

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CTI is primed for Vonjo’s commercial debut, Craig added. The company’s launch is “fully funded,” and CTI expects the drug to reach patients within 10 days.

Vonjo will carry a wholesale acquisition cost of $19,500 per month, CTI executives said on a call with investors Tuesday.

Given that the drug will run for roughly $240,000 per year before discounts, Vonjo could ultimately clinch $1 billion in peak sales among myelofibrosis patients with low platelets, analysts at BTIG wrote in a note to clients Tuesday.

Vonjo could help fill an unmet among myelofibrosis patients with severe thrombocytopenia, where other JAK2-focused therapeutics aren’t approved, the analysts said. That group represents roughly one-third of the more than 20,000 myelofibrosis patients in the U.S.

“We continue to believe Pacritinib has the potential to be a lead therapeutic in those MF patients with low platelets,” the BTIG team added.

The FDA based its approval on results from Vonjo’s late-stage PERSIST-2 study. Among patients who received Vonjo 200 mg—the dose covered in Monday’s approval—29% saw a reduction in spleen volume of at least 35%, versus just 3% of patients who were assigned best available therapy, including Novartis and Incyte’s Jakafi (ruxolitinib). Part and parcel to Vonjo’s accelerated approval, CTI will need to show clinical benefit in a confirmatory trial, the company said. On that front, CTI aims to complete its PACIFICA study by mid-2025.

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In PERSIST-2, meanwhile, Vonjo led to serious side effects in about 3% of patients, including anemia, thrombocytopenia, pneumonia, cardiac failure, disease progression, pyrexia and squamous cell carcinoma of the skin. Crucially, however, the drug doesn’t carry a black box warning for bleeding or cardiac events, CTI executives noted on Tuesday’s call.

Safety has been a major concern for the JAK class in recent months. The FDA added new warnings to the labels of marketed JAK inhibitors from Pfizer, AbbVie and Eli Lilly back in September, following a large postmarketing study of Xeljanz that linked the Pfizer drug to an increased risk of serious heart-related side effects in certain patients.

CTI has been awaiting Vonjo’s approval for several years, and the path to market hasn’t always been smooth. Back in 2016, the FDA slapped a clinical hold on Vonjo’s trials, asking CTI to modify protocols, among other actions, which the company agreed to do.

In 2018, the FDA told CTI to run another myelofibrosis phase 3 before filing for approval. The company in 2019 pulled Vonjo’s European filing for approval after learning the bloc’s Committee for Medicinal Products for Human Use was likely to reject the med