PharmaEssentia Corporation announced positive topline results from its Phase 3 SURPASS-ET clinical trial, evaluating ropeginterferon alfa-2b-njft (P1101), also known as Besremi, for patients with essential thrombocythemia (ET). The global, randomized, open-label study met its primary endpoint, demonstrating a durable clinical response in ET patients treated with P1101 compared to those treated with anagrelide.
The SURPASS-ET trial enrolled 174 patients, with 91 randomly assigned to the P1101 treatment group and 83 to the anagrelide group. The primary endpoint was a durable clinical response at months 9 and 12, as measured by modified European Leukemia Net (ELN) criteria. Key secondary endpoints included the change in JAK2 V617F allelic burden from baseline over time.
Primary Endpoint Achieved
The trial demonstrated a statistically significant improvement in durable clinical response with P1101. Among the intent-to-treat (ITT) population, 42.9% (39/91) of participants in the P1101 group achieved durable responses at months 9 and 12, compared to 6.0% (5/83) in the anagrelide group (p=0.0001). This indicates a significant benefit for patients receiving P1101 as a second-line therapy for ET.
Secondary Endpoint: JAK2 Allelic Burden
Secondary endpoint analysis showed a decrease in the JAK2 V617F allelic burden in the P1101 group. At baseline, the mean JAK2 allele burden was 33.7% in the P1101 group and 39.7% in the anagrelide group. After 12 months, the JAK2 allele burden in the P1101 group decreased to 25.3% (-8.4% change), while the anagrelide group saw a smaller reduction to 37.3% (-2.4% change). This suggests that P1101 may have a greater impact on addressing the underlying disease pathology compared to anagrelide.
Safety and Tolerability
The safety and tolerability profile of P1101 was manageable throughout the study. Treatment-related serious adverse events (TRSAEs) were less frequent in the P1101 arm, with two TRSAEs observed (2.2%) compared to eight (10%) in the anagrelide arm.
Expert Commentary
"We are extremely proud of the SURPASS-ET Phase 3 study outcome, which shows the potential of P1101 as an important new treatment option for patients with ET, a rare blood cancer that drastically increases the risk of heart attack or stroke," said Ko-Chung Lin, Ph.D., Founder and CEO of PharmaEssentia. "The data highlight the broad potential to apply our innovative monopegylated, long-acting interferon technology as a significant step forward for treating ET, and potentially other myeloproliferative neoplasms, with non-chemotherapy treatments."
Albert Qin, M.D., Ph.D., Chief Medical Officer of PharmaEssentia, added, "The results of the SURPASS-ET trial are significant. ET is a challenging condition associated with symptoms and risks of thrombosis and disease progression. These encouraging results highlight the potential of P1101 to provide an effective and tolerable new treatment option that we believe could provide a substantial clinical benefit for patients with ET."
Regulatory Plans and Future Studies
PharmaEssentia plans to present detailed clinical trial results, including additional pharmacokinetics and biomarker data, at a later date. The company intends to pursue regulatory discussions with the FDA to expand the existing label for P1101 to include a new potential indication of ET and anticipates regulatory submission by the end of 2025.
Additionally, PharmaEssentia is evaluating P1101 in ET patients in its EXCEED-ET (NCT05482971) clinical trial in North America. This Phase 2b clinical trial is a single-arm, multicenter trial designed to assess the efficacy, safety, and tolerability of P1101 in adult patients with ET. The company expects to present data from this clinical trial in the second half of 2025.
About Essential Thrombocythemia
Essential thrombocythemia (ET) is a chronic, rare blood disorder characterized by an overproduction of platelets in the blood, increasing the risk of thrombosis and hemorrhage. It is estimated that approximately 148,000 people in the U.S. have ET, with limited treatment options available to manage the condition and reduce the risk of disease progression.
