Pfizer ends its BMP9 pulmonary arterial hypertension bet
Pfizer has terminated PF-07868489, its phase 2 program in pulmonary arterial hypertension (PAH), closing down a long-running strategy built around the BMP9 pathway. The decision came on business grounds rather than safety or efficacy concerns, and it ends an open-label extension study that had been expected to continue into the second half of 2028.
The move lands hard because the program was not a casual side project. It grew out of an unusual biological premise: inhibiting BMP9 appeared to protect rodents against PAH, even though Pfizer initially explored BMP9 agonism before pivoting to antagonism as the field’s thinking shifted. In a disease defined by progressive pulmonary vascular remodeling, rising right-sided cardiac strain, and eventual heart failure risk, any signal that a vascular signaling pathway can be modulated toward protection tends to attract attention. Here, the company pulled back before a late-stage readout could test whether the preclinical logic would translate into a viable therapy for patients.
One sentence captures the full blow of the update: the program is over before a clinical verdict ever arrived.
Why BMP9 drew interest in PAH
BMP9 sits inside a pathway that has been viewed as biologically relevant to the pulmonary vasculature, where abnormal signaling can contribute to vessel remodeling and increased resistance. That made the target attractive for a disease in which the smallest changes in vascular tone and structure can have outsized hemodynamic consequences. When a pathway appears to influence the biology of the pulmonary artery wall, drug developers naturally ask whether enhancing or blocking it will reduce the pressure load that drives symptoms and long-term deterioration.
Pfizer’s trajectory on this target was especially notable because it moved in the opposite direction of its first instincts. The company had initially explored BMP9 agonists, then pivoted to antagonists after evidence emerged that inhibiting the protein might be beneficial. That kind of reversal usually reflects an evolving preclinical literature rather than a settled mechanistic consensus. It also illustrates the uncertainty that often surrounds first-in-class approaches in PAH, where signal transduction, endothelial integrity, and vascular proliferation are tightly linked and not always intuitive from the outset.
The phase 1/2 trial of PF-07868489 began in 2023, and a phase 2 open-label extension followed in 2025. By design, the extension would have provided a longer window to assess clinical durability, tolerability, and any emerging hints of efficacy in a chronic disease that requires sustained treatment rather than short bursts of intervention. Ending that follow-on study one year after it began leaves the program without the longer-term evidence that often separates a biologically plausible mechanism from a drug that can actually be used in practice.
A pipeline clear-out with broader strategic consequences
PF-07868489 was not the only asset removed from Pfizer’s portfolio in the quarterly update. The company also terminated PF-06835375, an anti-CXCR5 program, and later revealed that it had removed its ITP program and a phase 1 lupus study from the pipeline. Several other early assets were also cut, including two obesity candidates and two selective KRAS inhibitors in solid tumor trials.
Those additional changes matter because they show a broader commercial pruning rather than an isolated disappointment in one disease area. Pfizer is trimming multiple mid-phase and early-stage assets across distinct therapeutic classes, a pattern that suggests sharper internal pressure to prioritize programs with a clearer path to differentiated value. For PF-07868489, the company explicitly cited business reasons, which places the termination in the context of portfolio management rather than any disclosed concern that the drug was unsafe or ineffective.
The distinction between a business decision and a scientific one is not semantic. In a competitive PAH field, development costs can climb quickly, and a program that still lacks late-phase proof may be harder to defend when capital is being reassigned to assets with stronger commercial or clinical momentum. PF-07868489 had a mechanistic rationale, but it did not yet have the kind of clinical validation that can justify carrying an expensive chronic-disease program deeper into development.
What the termination means for PAH drug development
PAH remains a disease where therapy has repeatedly advanced by targeting vascular biology rather than symptoms alone. Endothelin, nitric oxide, and prostacyclin pathways already anchor much of modern care, but the field still needs new mechanisms that can alter the disease course more effectively or with better tolerability. BMP9 offered one such avenue because it was tied to pulmonary vascular signaling in a way that looked experimentally tractable. Pfizer’s retreat does not invalidate the biology, yet it does remove one of the more unusual development efforts in the space.
The deeper challenge is that PAH drug development rarely fails for a single reason. A target can look compelling in rodents and still stumble when exposed to human disease heterogeneity, comorbidities, background therapy, and the long horizon required to show meaningful benefit. Patients with PAH often live with combination treatment, variable hemodynamics, and progressive right ventricular stress, so a candidate must do more than shift a pathway in isolation. It must prove that the pathway shift translates into durable clinical value.
Pfizer’s decision leaves that question unanswered for BMP9 antagonism in PAH. No efficacy problem was disclosed, and no safety concern was cited, but the absence of a clinical readout means the field loses a development program before it could establish whether the biological hypothesis was worth carrying forward.
Business discipline, not bedside closure
The open-label extension had been scheduled to run until the second half of 2028. Ending it now compresses the timeline and signals a hard portfolio choice, one that prioritizes resource allocation over prolonged exploration. For patients and clinicians, the practical consequence is simple: another experimental route to PAH treatment has been shut off before the evidence base matured.
Pfizer’s third-quarter pipeline update now reads as a broader reset, with PAH joining obesity, autoimmune, and oncology programs on the chopping block. The company has not disclosed any clinical problem with PF-07868489, and that leaves the most important unresolved issue squarely at the level of translational medicine: whether BMP9 modulation could still prove useful in PAH if another sponsor, or another dataset, were to carry it further.