Protagonist Therapeutics, Inc. announced details from five abstracts at the American Society of Hematology 2023 Annual Meeting, including an oral presentation with two-year follow up data from the Phase 2 REVIVE study with rusfertide, a mimetic of the natural hormone hepcidin with potential therapeutic value in the treatment of polycythemia vera (PV) and other disease indications. Ellen K. Ritchie, M.D., Associate Professor of Clinical Medicine at Weill Cornell Medical College presented long-term follow up data from patients in REVIVE who continued into the open label extension (OLE). The Phase 2 trial consisted of 3 parts including 70 patients in the dose-finding Part 1, 59 patients in the placebo-controlled, randomized withdrawal Part 2, and 58 patients in the OLE.

At the end of Part 2, 69% (18/26) of rusfertide patients achieved hematocrit control and remained phlebotomy free at 12 weeks, compared to only 19% (5/27) on placebo (p=0.0003). Among the 58 patients that continued into the OLE, as of October 17, 2023 (data cut-off for the ASH presentation), 57 had been treated for over one year and 37 had been treated for over two years. The median follow-up was 2.1 years and data were provided out to 2.5 years in 21 patients.

Results showed that rusfertide when added to therapeutic phlebotomy with or without cytoreductive therapy through 2 years resulted in: long-term durable control of hematocrit well below the 45% threshold, decreased red blood cell counts and decreased phlebotomy use; improved and normalized serum ferritin levels; and no new safety signals, with the majority of adverse events being grade 1-2 injection site reactions that decreased in frequency over time, or adverse events consistent with comorbidities anticipated in the PV population Cancers are common in PV patients and in REVIVE, 19 of 70 patients (27.1%) had a history of cancer prior to enrolling in the study. Among these patients, 10 (14.3%) had a history of skin cancer. As of October 17, 2023, there have been 8 patients diagnosed with cancer while on study and 7 (7/70; 10.0%) with skin cancer.

A separate poster presented at ASH by Dr. Naveen Pemmaraju, of MD Anderson Cancer Center titled "Prevalence of Second Cancers in Patients with Polycythemia Vera (PV): A Retrospective Analysis of US Real-World Claims Data," utilized data for 2007-2019 from a large US electronic health records database to examine the overall frequency of secondary cancers in patients with a primary PV diagnosis and compared those who were treated with hydroxyurea (HU) versus phlebotomy (PHL). None of these patients had received rusfertide. Among the 20,089 PV patients that qualified for this retrospective study: 35.7% (7,181) of patients reported at least one secondary cancer 9.1% (1,830) of patients reported any form of skin cancer 8.3% (1,659) of patients reported non-melanoma skin cancer The mechanisms contributing to the increased risk of cancers in PV patients are not well understood.

However, the subset of PV patients treated with HU in this study of real-world claims data had nearly twice the rate of cancers compared to phlebotomy-only treated patients. In an oral presentation, Dr. Andrew T. Kuykendall, of Moffitt Cancer Center in Tampa, FL discussed a real-world retrospective analysis indicating that PV patients (not treated with rusfertide) experience high rates of arterial and venous TEs (25%). High-risk patients (classified by age or event-based risk) showed a higher risk of death than lower risk PV patients (37% vs 8.5%, respectively).

The study included over 20,000 PV patients in the US via the Optum MarketClarity Database. TE incidence was highest among event-based high-risk patients (50.2%; 1634/3256), followed by age-based high-risk (25.0%; 2480/9924) and low-risk patients (13.3%; 921/6909).