FDA has approved ropeginterferon alfa-2b-njft (Besremi) for adults with essential thrombocythemia (ET), making it the first new FDA-approved treatment for the rare blood cancer in nearly three decades, PharmaEssentia USA, a subsidiary of PharmaEssentia, announced August 31, 2026.¹ Ropeginterferon alfa-2b is now approved for adults with ET regardless of genotype or disease status, including newly diagnosed patients who have not yet received cytoreductive therapy.
Key facts
- Drug: Ropeginterferon alfa-2b-njft (Besremi; PharmaEssentia)
- Class: Long-acting, monopegylated interferon-based therapy
- Indication: Essential thrombocythemia (ET), adults, any genotype/disease status
- Trial: SURPASS-ET (NCT04285086); phase 3, 174 patients
- Key data: 43% durable modified ELN response vs 6% for anagrelide
- Additional benefit: Reduced thromboembolic events over 12 months vs anagrelide
- Regulatory status: FDA-approved August 31, 2026; first new ET therapy in ~30 years
- Prior designations: US orphan drug status (polycythemia vera [PV] and ET)
- Existing approval: Also PV in the US
- Geography: Also approved for ET in Japan and Taiwan
"For nearly 30 years, people living with ET and the physicians treating them have had limited treatment innovation," said Ruben Mesa, MD, principal investigator of the SURPASS-ET trial and president of Advocate Health's Cancer National Service Line, in a company press release.1 "The approval of BESREMi provides an important new treatment option that is supported by strong clinical evidence and that also works at the source of the disease rather than solely managing symptoms."
What clinical data support the approval?
Approval was based on the global phase 3 SURPASS-ET trial (NCT04285086), which evaluated ropeginterferon alfa-2b in patients with ET and leukocytosis who were intolerant or resistant to hydroxyurea.¹ In the trial, which randomized 174 patients to ropeginterferon alfa-2b or anagrelide, 43% of patients receiving ropeginterferon alfa-2b achieved a durable modified European LeukemiaNet (ELN) response at months 9 and 12, compared with 6% of those receiving anagrelide.² Ropeginterferon alfa-2b also reduced thromboembolic events over 12 months of treatment compared with anagrelide.¹ A separate US multicenter study, EXCEED-ET, evaluated ropeginterferon alfa-2b across ET patients with different driver mutations.³
Why is a new treatment needed for ET?
ET is a rare, chronic blood cancer marked by overproduction of platelets in the bone marrow, often driven by mutations such as Janus kinase 2, and patients face an increased risk of blood clots, abnormal bleeding, and enlarged spleen. Patients with ET often require years of ongoing disease management and remain at risk for serious complications, including heart attacks, strokes, and pulmonary embolism. Current therapies primarily focus on controlling platelet counts and symptoms, with limited impact on the disease's underlying biology.¹
How does ropeginterferon alfa-2b work?
Ropeginterferon alfa-2b is a long-acting interferon-based therapy that uses monopegylation technology and an extended half-life to target disease-driving cells in the bone marrow while reducing elevated platelet counts and overall disease burden.¹
"Being able to hit [multiple] targets at once is so critically and verifiably important to ameliorate [disease], and that's what we believe is going to be a transformation in [a rare disease] condition," said Howard Berman, PhD, CEO of ReAlta Life Sciences, as he pointed out a different rare-disease drug candidate's multi-pathway design in a previous interview with BioPharm International®.⁴
The current FDA approval expands ropeginterferon alfa-2b's existing US label, which has been used commercially to treat adults with polycythemia vera (PV), another myeloproliferative neoplasm.¹ The therapy holds orphan drug designation in the United States for both PV and ET, and this latest approval follows earlier regulatory approvals for the ET indication in Japan and Taiwan.¹
What are the limitations?
The pivotal SURPASS-ET trial was open-label rather than blinded and compared ropeginterferon alfa-2b specifically against anagrelide in a hydroxyurea-intolerant or -resistant population, rather than against a broader range of comparators or a treatment-naive population overall. Long-term outcomes beyond 12 months of follow-up have not yet been reported.
References
- PharmaEssentia USA. FDA approves PharmaEssentia's BESREMi (ropeginterferon alfa-2b-njft) for adults with essential thrombocythemia, a rare blood cancer. Press release. Published August 31, 2026. Accessed August 31, 2026. https://us.pharmaessentia.com/fda-approves-pharmaessentias-besremi-ropeginterferon-alfa-2b-njft-for-adults-with-essential-thrombocythemia-a-rare-blood-cancer/
- Mesa R, Gill H, Zhang L, et al; SURPASS-ET Study Group. Ropeginterferon alfa-2b in hydroxyurea-intolerant or hydroxyurea-refractory essential thrombocythaemia (SURPASS ET): a multicenter, open-label, randomized, active-controlled, phase 3 study. Lancet Haematol. 2025;12(11):e862-e875. doi:10.1016/S2352-3026(25)00264-9
- Reeves BN, El Chaer F, Foltz L, et al. Ropeginterferon alfa-2b-njft treatment in essential thrombocythemia across different driver mutations: results from a North American, single-arm, multicenter study (EXCEED-ET). Lancet Reg Health Am. 2026;61:101529. doi:10.1016/j.lana.2026.101529
- Jacobus N, Berman H, Mirasol F. ReAlta CEO, Dr Howard Berman, discusses how complement, neutrophil, and myeloperoxidase inhibition may transform HIE treatment. BioPharm International. Published June 25, 2026. Accessed August 31, 2026. https://www.biopharminternational.com/view/realta-ceo-howard-berman-complement-neutrophil-myeloperoxidase-inhibition-hie
