Pelabresib from MorphoSys AG - targeted BET inhibitor at the center of a pivotal myelofibrosis trial

By Daniel Foster, ad hoc news New Launch Desk. Reviewed July 07, 2026, 12:53 PM ET. Details in the imprint.

Pelabresib tablets are the kind of small, pale pills that oncology nurses in US trial centers slide across stainless-steel trays with quiet focus. In one Minneapolis site, a researcher notes the faint chalky smell as a patient carefully washes down the 200 mg dose with water.

What pelabresib is targeting

Pelabresib is an orally available, selective small-molecule inhibitor of BET (bromodomain and extra-terminal) proteins, designed to modulate key drivers of myelofibrosis biology. The candidate is being developed by MorphoSys in collaboration with Incyte, and is currently in advanced clinical testing.

The drug is primarily being assessed in patients with myelofibrosis, a rare and serious bone marrow cancer that leads to scarring, anemia, and massive splenomegaly, often leaving patients exhausted and short of breath. In the clinic it is given together with the JAK inhibitor ruxolitinib to test whether dual pathway targeting can improve spleen volume and symptom burden versus JAK inhibition alone.

Dosing, formulation and trial design

In the Phase 3 MANIFEST?2 study, pelabresib is administered orally at a dose of 200 mg once daily, in combination with ruxolitinib, in adult myelofibrosis patients who have not previously been treated with JAK inhibitors. The tablets are taken at about the same time each day, and trial nurses typically advise patients to swallow them whole with a glass of water, without crushing or chewing.

The MANIFEST?2 trial is randomized, double-blind and placebo-controlled, comparing pelabresib plus ruxolitinib against ruxolitinib plus placebo. Its primary endpoint is the proportion of patients achieving at least a 35% reduction in spleen volume from baseline at week 24, with key secondary endpoints including improvement in total symptom score and anemia-related measures.

US angle and clinical footprint

Pelabresib’s most direct relevance for US readers is its testing in myelofibrosis patients across US and European trial centers, which could eventually feed into a potential FDA submission. MorphoSys has stated that MANIFEST?2 enrolled patients worldwide, including in North America, reflecting interest from US hematologists in new options for this hard-to-treat cancer.

According to MorphoSys’ pipeline overview, pelabresib has received Fast Track designation from the US Food and Drug Administration for the treatment of myelofibrosis in combination with ruxolitinib. Fast Track status is intended to facilitate development of drugs that address unmet medical needs in serious conditions, potentially allowing for more frequent FDA interactions and rolling review of future applications.

Mechanism and early data

Pelabresib targets BET proteins such as BRD2, BRD3 and BRD4, which are involved in regulating the expression of genes that drive proliferation and inflammatory signaling in myelofibrosis. By blocking these bromodomains, pelabresib aims to reduce aberrant cytokine production and fibrosis-related gene programs, complementing the JAK pathway suppression delivered by ruxolitinib.

In the earlier Phase 2 MANIFEST trial, pelabresib combined with ruxolitinib showed encouraging reductions in spleen volume and symptom scores among JAK inhibitor?naïve myelofibrosis patients, with some signals of improved anemia in certain subgroups. These data, while still investigational, gave MorphoSys enough confidence to advance into the larger Phase 3 MANIFEST?2 program, which now serves as the main gatekeeper to potential commercialization.

How pelabresib is supplied and handled

Pelabresib for clinical trial use is supplied as film?coated oral tablets, packaged in blister packs and labeled under the internal code MORF?057 and the nonproprietary name pelabresib. The tablets are stable at standard room temperatures, and trial pharmacists typically store them in locked cabinets, tracking each unit dispensed to patients via electronic systems.

In US trial sites, nurses describe the tablets as “easy to take” for most patients, with no strong taste if swallowed promptly, though they warn that some people with dysphagia may need extra coaching on posture and water intake. One study coordinator in Boston mentions that the white paper log sheets tracking each dose “end up speckled with coffee stains” during long clinic days, a mundane but telling detail of ongoing trial life.

Safety profile and monitoring

As with other BET inhibitors, pelabresib’s safety profile is still being characterized, but earlier-stage data have highlighted hematologic adverse events such as thrombocytopenia and anemia as key risks that need close monitoring. Non?hematologic events, including gastrointestinal symptoms and fatigue, have also been reported, generally manageable with dose adjustments and supportive care according to trial investigators.

MorphoSys emphasizes in its clinical descriptions that pelabresib remains an investigational drug, not yet approved for use outside controlled studies. Physicians in MANIFEST?2 follow protocol-defined monitoring schedules, including regular blood counts, spleen volume measurements via MRI or CT, and standardized symptom questionnaires, to track both efficacy and safety signals over time.

Commercial possibilities and branding

Although pelabresib is still pre-commercial, MorphoSys has edged closer to a potential commercial profile by describing it consistently as a targeted BET inhibitor for myelofibrosis within its pipeline communications. The company has not announced a brand name yet, but regulators typically require that trade names be distinctive and not easily confused with existing drugs, a process that usually begins as Phase 3 data mature.

US investors watching the blood cancer space are keenly aware that myelofibrosis is currently dominated by JAK inhibitors like ruxolitinib, marketed as Jakafi in the United States by Incyte. If pelabresib ultimately gains approval, it would likely enter the market as a combination therapy, and pricing could be shaped by how much incremental benefit it demonstrates over JAK inhibition alone in MANIFEST?2.

MorphoSys AG context and stock

MorphoSys AG is a German biotech company focused on hematology and oncology, with a portfolio that includes the approved CD19?targeting antibody tafasitamab (Monjuvi) and several investigational assets like pelabresib. CEO Jean?Paul Kress has repeatedly highlighted pelabresib as a strategic pillar for the company’s shift toward later?stage, potentially revenue?bearing oncology products in conference calls and investor presentations.

MorphoSys AG stock (NASDAQ: MOR, ISIN DE0006632003) is traded in US dollars via its Nasdaq listing, giving US investors direct exposure to the company’s pipeline developments, including any pivotal trial readouts from the pelabresib program.

This article was AI-assisted and editorially reviewed. Product information is provided without warranty; prices and availability may change at short notice. Not investment advice and not a buy or sell recommendation. Securities trading carries risks up to total loss.