Flagship oncology bet, pelabresib targets myelofibrosis patients for MorphoSys

Edited by ad hoc news Flagship & Bestseller Desk. Reviewed before publication on 06/15/2026 at 10:47 PM ET. Details in the imprint.

For MorphoSys, the oral BET inhibitor pelabresib, also known by the development code CPI-0610, has become the flagship oncology program the company is pushing toward potential registration in myelofibrosis. The small-molecule drug is being tested as an add-on to standard JAK inhibitor therapy with the goal of improving both spleen volume reduction and symptom control in patients with intermediate- and high-risk disease, positioning pelabresib as a centerpiece of MorphoSys’s late-stage pipeline on the company’s official pelabresib pipeline page.

How pelabresib is designed to work alongside JAK inhibition

Pelabresib belongs to the class of bromodomain and extra-terminal domain (BET) inhibitors, which are intended to modulate gene expression programs that drive malignant cell proliferation and inflammatory signaling in myelofibrosis. Unlike JAK inhibitors that primarily target signaling pathways downstream of cytokine receptors, BET inhibitors such as pelabresib are aimed at the epigenetic machinery that regulates transcription of multiple disease-relevant genes, which could theoretically translate into broader effects on spleen size, symptoms, anemia and bone marrow fibrosis when used in combination.

The drug is administered orally, a practical advantage for chronic treatment in a population that already faces heavy symptom burden and frequent monitoring requirements. Morphologically, myelofibrosis is characterized by bone marrow scarring, extramedullary hematopoiesis and massive splenomegaly; the current standard therapies, including ruxolitinib and other JAK inhibitors, can shrink the spleen and improve constitutional symptoms but are often limited by cytopenias and incomplete responses. MorphoSys has consistently framed pelabresib as a potential complement rather than a replacement for JAK inhibition, focusing its development strategy on combinations rather than monotherapy in key trials.

The pivotal MANIFEST-2 study is central to this strategy. Designed as a randomized, double-blind, Phase 3 trial in JAK inhibitor-naive myelofibrosis patients, MANIFEST-2 evaluates pelabresib plus ruxolitinib versus ruxolitinib plus placebo, with the primary endpoint defined as a spleen volume reduction of at least 35 percent at week 24, a standard benchmark in this indication frequently used for regulatory assessment. The trial also tracks secondary endpoints including symptom score improvements and safety profiles, which will be closely watched by clinicians given the concerns around overlapping toxicities and the need for regimens that patients can tolerate over long treatment horizons.

In earlier-phase MANIFEST cohorts, MorphoSys and its partners reported signals of activity for pelabresib in combination with ruxolitinib, including rates of spleen volume reduction and symptom improvements that the company has characterized as encouraging compared with historical expectations for JAK inhibition alone. While cross-trial comparisons are inherently limited, these data provided the rationale for moving into Phase 3 and have been cited by MorphoSys in scientific forums and investor communications as evidence that targeting epigenetic regulation could enhance the benefits of established pathway inhibitors. Analysts following hematology drug development have also noted the interest of key opinion leaders in the potential of BET inhibition to address residual disease manifestations that JAK inhibitors leave untreated.

Access to pelabresib at this stage remains restricted to clinical trials, typically offered at specialized oncology and hematology centers in North America, Europe and selected additional regions that participate in the MANIFEST and MANIFEST-2 programs. Because the compound has not yet been approved by regulators, there is no commercial list price, and MorphoSys shoulders the cost of supplying drug to trial participants as part of its broader research and development budget for hematologic malignancies. The company has highlighted myelofibrosis as an area of significant unmet need, pointing out that many patients eventually lose response to JAK inhibitors or cannot tolerate them, which leaves a gap for new modalities that can be layered on top of or sequenced after existing options.

Strategically, pelabresib sits at the core of MorphoSys’s ambition to evolve from a primarily antibody-focused biotech into a broader oncology player with both small-molecule and biologic assets in diseases such as myelofibrosis and other blood cancers. The company has divested or partnered parts of its legacy portfolio in recent years to concentrate capital and scientific resources on late-stage assets, with pelabresib frequently cited by management as one of the main drivers of potential future value creation if Phase 3 data and regulatory reviews are favorable. According to a recent overview of the program, pelabresib is one of the most advanced BET inhibitors in clinical development for myelofibrosis, underscoring MorphoSys’s high conviction in this mechanism of action and the commercial opportunity if the combination with ruxolitinib can deliver clinically meaningful benefits over standard therapy as summarized in an ad hoc news program profile.

Against this backdrop, MorphoSys’s equity story is increasingly tied to the outcome of pelabresib’s late-stage trials and the broader market reception in myelofibrosis and potentially related indications. The company is publicly listed in Germany, and its shares trade on the Frankfurt Stock Exchange under the ISIN DE0006632003, giving investors direct exposure to the clinical and commercial trajectory of its oncology pipeline, including pelabresib as the current flagship candidate.

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