Pfizer Stops Development of Novel PCSK9 Inhibitor, Halts Ongoing Trials

Deborah Brauser

November 01, 2016

The global development program for the investigational proprotein convertase subtilisin kexin type 9 (PCSK9) inhibitor bococizumab (Pfizer) will be discontinued because clinical data show that it's "not likely to provide value to patients, physicians, or shareholders," according to a statement released today from the drug's manufacturer.

In addition, the manufacturer will be applying the brakes to two of its ongoing trials.

The injectable drug was designed to reduce low-density lipoprotein cholesterol (LDL-C) while also improving cardiovascular (CV) outcomes. No country had yet granted it regulatory approval.

A total of eight phase 3 Studies of PCSK9 Inhibition and the Reduction of Vascular Events (SPIRE) were created by Pfizer's development program, including two ongoing CV outcomes trials.

The six completed SPIRE studies focused on lipid-lowering. Data from four showed that all primary endpoints were met — as did top-line results from the remaining two.

However, the manufacturer noted that after review of all the findings from these completed studies, there was "an emerging clinical profile that includes an unanticipated attenuation of [LDL-C] over time, as well as a higher level of immunogenicity and higher rate of injection-site reactions" with the novel drug compared with other drugs in the same class.

In addition to stopping any further development of the drug, the company has decided to halt the SPIRE-1 and SPIRE-2 morbidity and mortality studies.

"We are disappointed with this outcome but remain committed to investing in innovation, concentrating our pipeline on areas where we can bring transformational therapies to address unmet needs," James Rusnak, MD, PhD, chief development officer of cardiovascular and metabolic diseases at Pfizer Global Product Development, said in a release.

Data to Be Released

As reported previously by heart wire by Medscape, the SPIRE-AI trial met its primary endpoints — as did the SPIRE-SI, SPIRE-HR, and SPIRE-FH trials. And top-line results from the SPIRE-LDL and SPIRE-LL trials showed significant reductions in baseline lipid levels at 12 weeks for bococizumab vs placebo in adults who had primary hyperlipidemia or mixed dyslipidemia, were at high or very high risk for CV events, and were taking statins.

The drug was considered to be "generally safe and well-tolerated" in all of the trials, but "an evaluation of cross-reactivity to other PCSK9-inhibitor monoclonal antibodies was not suggestive of clinically important concerns," states the company.

Pfizer will be making the data from the halted trials available to study leaders "to honor the altruism of trial participants and to maximize the clinical and scientific knowledge," Paul M. Ridker, MD, co-chair of the SPIRE program's executive committee and director for CV Disease Prevention at Brigham and Women's Hospital in Boston, Massachusetts, noted in the release.

Study participants are instructed to speak with their study physicians if they have any questions.

The US Food and Drug Administration first approved a PCSK9 inhibitor for lowering LDL-C in July 2015, when it approved alirocumab (Praluent, Sanofi/Regeneron). One month later, it gave the greenlight to evolocumab (Repatha, Amgen) for the same indication.

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