Haematology-Oncology · Clinical trials
Myelofibrosis Clinical Trials
Approved therapies, the pivotal-trial endpoints they were judged on, the magnitude of benefit — and the drugs that failed their endpoints, and why.
Indication overview
About myelofibrosis — and why its trials are hard
Myelofibrosis is a chronic myeloproliferative neoplasm characterized by bone-marrow scarring (fibrosis), splenomegaly, constitutional symptoms, and progressive cytopenias, often driven by JAK2, CALR, or MPL mutations that activate JAK-STAT signaling. It can arise de novo (primary) or evolve from polycythemia vera or essential thrombocythemia. Risk is assessed with DIPSS and molecularly enhanced scores, and allogeneic stem-cell transplant remains the only curative therapy. JAK inhibitors are the mainstay of medical management: ruxolitinib, the first approved, reduces spleen size and symptom burden and improves survival; fedratinib is a second-line and frontline option. For patients with thrombocytopenia, pacritinib enables treatment at low platelet counts, and for those with anemia, momelotinib uniquely improves anemia and transfusion needs alongside spleen and symptom control. Endpoints center on spleen volume reduction (SVR35) and total symptom score (TSS50), with transfusion independence increasingly important. Many combination and next-generation agents have failed to add benefit to a JAK-inhibitor backbone, though the field continues to pursue disease-modifying therapy.
Approved therapies & pivotal evidence
What's been approved — and by how much it moved the endpoint
| Drug (brand) | Approved | Setting | Pivotal trial | Primary endpoint | Magnitude of benefit |
|---|---|---|---|---|---|
| Ruxolitinib (Jakafi) | 2011 | Intermediate/high-risk myelofibrosis (first-line) | COMFORT-I and COMFORT-II | Spleen volume reduction >=35% (SVR35) | SVR35 ~42% vs ~1% placebo (COMFORT-I); symptom improvement and later OS advantage |
| Fedratinib (Inrebic) | 2019 | Intermediate-2/high-risk myelofibrosis (first-line or post-ruxolitinib) | JAKARTA (post-rux: JAKARTA-2) | Spleen volume reduction >=35% (SVR35) | SVR35 ~37% at 24 weeks vs ~1% placebo (JAKARTA) |
| Pacritinib (Vonjo) | 2022 | Myelofibrosis with severe thrombocytopenia (platelets <50,000) | PERSIST-2 | Spleen volume reduction >=35% (SVR35) | SVR35 ~29% vs ~3% best available therapy in thrombocytopenic patients (accelerated approval) |
| Momelotinib (Ojjaara) | 2023 | Myelofibrosis with anemia | MOMENTUM (and SIMPLIFY-1) | Symptom response (TSS), spleen response, transfusion independence | TSS50 ~25% vs ~9% danazol; ~31% transfusion-independent with spleen and symptom benefit |
Where trials have failed
Drugs that missed their endpoint — and what contributed
The most instructive lessons in myelofibrosis development come from programmes that failed the endpoint that mattered.
| Drug / trial | Endpoint outcome | What contributed |
|---|---|---|
| Momelotinib (earlier development) — SIMPLIFY-2 | Failed to demonstrate spleen response superiority vs best available therapy in ruxolitinib-treated patients | Comparator arm largely continued ruxolitinib; endpoint design and prior JAK-inhibitor exposure obscured benefit before MOMENTUM secured approval |
| Imetelstat (telomerase inhibitor) — IMbark / MYF2001 | Did not meet co-primary spleen and symptom response endpoints in relapsed/refractory MF | Limited SVR35 and TSS response; development in MF de-prioritized in favor of lower-risk MDS |
| Pomalidomide — RESUME | Failed to significantly improve myelofibrosis-associated anemia/transfusion independence vs placebo | No meaningful red-cell response benefit over placebo in transfusion-dependent patients |
Choosing the right endpoint
Primary endpoints that matter in myelofibrosis trials
- Spleen volume reduction >=35% (SVR35) — Primary registration endpoint for JAK inhibitors, measured by MRI/CT at 24 weeks
- Total symptom score reduction >=50% (TSS50) — Patient-reported constitutional symptom improvement; key co-primary endpoint
- Transfusion independence — Central to momelotinib's differentiation; reflects anemia benefit
- Overall survival (OS) — Longer-term COMFORT follow-up suggested a survival advantage with ruxolitinib
- Anemia response / platelet count tolerance — Guides drug selection (momelotinib for anemia, pacritinib for thrombocytopenia)
How iNGENū runs myelofibrosis trials
Physician-led design, built for FDA submission
Endpoint & biomarker strategy
Board-certified specialists design endpoints and patient selection aligned to current FDA guidance for this indication.
FDA-ready data
Built to ICH-GCP and 21 CFR 312.120, with direct FDA submission — data accepted by the FDA, EMA and MHRA.
Faster, lower-cost delivery
~4-week ethics via the TGA CTN scheme, up to 43.5% R&D rebate, and 80–90% below US CRO cost.
Request a fixed-milestone proposal and a tailored endpoint & feasibility summary for this indication.
Frequently asked questions
Myelofibrosis clinical trials — FAQs
What are JAK inhibitors and why are they central to myelofibrosis?
How are treatment choices tailored to blood counts?
Is a cure possible for myelofibrosis?
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