P1101 Treatment Meets Phase 3 Primary End Point in Essential Thrombocythemia

Among patients with essential thrombocythemia (ET), treatment with ropeginterferon alfa-2b-njft (P1101) generated durable hematologic responses with a manageable safety profile and a lower rate of treatment-related serious side effects, meeting the primary end point of the phase 3 SURPASS-ET trial.

The data, which were shared in a press release from PharmaEssentia Corporation, showed that among the intent-to-treat population (91 patients), 42.9% of patients achieved durable responses at months 9 and 12 versus 6% of patients who were treated with anagrelide on the comparator group (83 patients). Furthermore, the treatment exhibited a manageable safety profile. Among participants treated with P1101, 2.2% of patients exhibited treatment-related serious side effects compared with 10% in the anagrelide arm.

“We are extremely proud of the phase 3 SURPASS-ET 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,” Dr. Ko-Chung Lin, Founder and CEO of PharmaEssentia, said in the press release. “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. We plan to leverage these data to expand the existing P1101 product label and further expand the reach of P1101 to address this growing global unmet medical need.”

More Information on the SURPASS-ET Clinical Trial

The global, randomized, open-label, active-controlled SURPASS-ET study is evaluating the efficacy, safety and tolerability of P1101 versus anagrelide in the second-line setting for patients with ET for 12 months. In total, 174 patients were enrolled onto the clinical trial consisting of 91 patients who were randomly assigned to the P1101 treatment group and 83 to the anagrelide group.

The press release emphasizes that P1101 may have a greater impact on addressing the underlying disease pathology compared with anagrelide. This is because, at baseline, the JAK2 V617F allelic burden decreased from 33.7% to 25.3% (-8.4% change) at 12 months in the P1101 group compared with a reduction of 39.7% to 37.3% (-2.4% change) in the anagrelide group.

The company goes on to say that they plan to present detailed clinical trial results at a later date. They also plan to pursue regulatory discussions with the FDA on the expansion of the existing label to include a new potential indication of ET; regulatory submission is anticipated by the end of 2025.

Other Indications of P1101 and Future Directions with the Agent

Currently, ropeginterferon alfa-2b-njft is approved by the FDA and marketed as Besremi® under an indication for polycythemia vera. However, the planned label expansion will also include patients with ET. The chronic, rare blood disorder is the most common type of myeloproliferative neoplasm, and is often caused by genetic mutations which can cause the bone marrow to produce too many platelets. In turn, this may obstruct blood flow and cause a stroke, heart attack or pulmonary embolism. In the U.S. it is estimated that approximately 148,000 people have ET, which impacts quality of life due to burdensome symptoms. Individuals who are diagnosed with this disease have limited treatment options to manage their condition and reduce the risk of thrombosis and slowing disease progression. Therefore, investigators are evaluating P1101 as a potential treatment option.

The investigative agent is an innovative monopegylated, long-acting interferon and, with its unique pegylation technology, has a long duration of activity in the body. The current dosing schedule for the agent allows for flexible dosing that helps meet the individual needs of patients, according to the press release.

Moreover, the company shared that they are also evaluating P1101 in patients with ET in the phase 2b EXCEED-ET study in North America. This single-arm, multicenter clinical trial is evaluating the efficacy, safety, and tolerability of the agent in adult patients with ET. Data from this clinical trial is expected to be presented in the second half of 2025, the release noted.

“The results of the SURPASS-ET trial are significant,” Dr. Albert Qin, Chief Medical Officer of PharmaEssentia, concluded in the press release. “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. We plan to submit these results to the FDA and other regulatory agencies as soon as possible in hopes of providing this potential new treatment option to patients with ET.”

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