UCSF Details How FDA's Bone Density Endpoint Will Shrink Osteoporosis Trials

This article is based on UCSF News' report of the research. The underlying paper was not reviewed.

The scale of the change is large. According to UCSF News, a typical Phase 3 trial has enrolled 6,000 to 15,000 patients for three to five years, so that enough fractures occur to judge whether a drug works. Under the new approach, trials can enroll about 750 patients and follow them for a year and a half to two years.

For now, the change covers trials in postmenopausal women with osteoporosis, UCSF News reports. The FDA made the decision late last year.

The market logic is plain, though it is interpretation rather than reporting. Smaller and shorter pivotal trials should cost less. A lower cost of entry could draw in new bone-drug developers, including smaller firms that could not fund a multiyear fracture trial. It could also create openings for licensing deals and acquisitions. UCSF News does not make these forecasts itself.

What UCSF News does report is that development had stalled. Dennis Black, PhD, a UCSF professor of epidemiology and biostatistics and co-lead of the SABRE Project, said the most recent osteoporosis drug approval was romosozumab in 2019. He said no new drugs have entered the pipeline since then because of the expense and time required. "Everything just stopped," he said.

The demand side is sizable. According to UCSF News, osteoporosis affects about 10 million Americans over age 50, including 1 in 5 women. The report says the share of Americans 65 and older is expected to rise from 18.9% to 23.4% by 2060.

The evidence behind the decision came from SABRE, the Study to Advance Bone Mineral Density as a Regulatory Endpoint. UCSF News describes it as a publicprivate collaboration of academia, the National Institutes of Health, the FDA, industry and nonprofits. Black said the team assembled data from more than 50 randomized trials involving about 170,000 patients, much of it held by private companies.

Black said the analysis found a strong link between larger bone density gains and larger fracture reductions. According to UCSF News, when a drug raised bone density above a certain threshold, there was more than a 95% chance it reduced fractures. He said this held across drugs that work in different ways, some slowing bone breakdown and others building bone.

Incumbents may face more competition. Black said new drugs could differ in dosing, duration and side effects, and that more competition could mean lower prices and better access. He framed this as a hope, not a certainty. Existing drugs work, he said, but some patients have rare side effects or find dosing inconvenient.

The precedent may matter beyond bones. UCSF News describes bone density as the first surrogate endpoint the FDA has formally qualified in any therapeutic area since its formal biomarker qualification process began. Black said the acceptance could set a precedent for faster development in areas such as cancer or Alzheimer's disease. That is his view. The report does not say whether the FDA will treat other endpoints the same way.

UCSF News describes the change as more than a decade in the making. Black named two hurdles: gathering the data and moving through an FDA process with no close precedent and several levels of review. Other disease areas would likely face similar work.

Watch for the first pivotal osteoporosis trials designed around the bone density endpoint. The UCSF report does not say whether any are under way, so the first announcements and financing deals will show how quickly the market responds.

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