Scholar Rock’s Apitegromab Filing Exposes the CMO Due Diligence Gap That Keeps Burning Sponsors

Pull up Warning Letter 320-26-20, issued November 20, 2025, to Catalent Indiana, LLC. The FDA inspected the Bloomington, Indiana sterile drug manufacturing facility for twenty-one days, from June 23 to July 14, 2025, and what inspectors found was serious enough to warrant one of the most consequential compliance designations the agency issues: Official Action Indicated. Now look at Scholar Rock’s apitegromab program, a Biologics License Application for a spinal muscular atrophy treatment with a PDUFA date of September 30, 2026. The company just dropped that Bloomington facility from its BLA refiling. The question every clinical operations executive should be sitting with is not whether Scholar Rock made the right call. They obviously did. The question is: how did a facility this far into the compliance danger zone end up on the manufacturing roster of a late-stage rare disease program in the first place?

That question has an uncomfortable answer, and it implicates the entire contract manufacturing due-diligence framework that sponsors rely on when they are racing toward a BLA.

The Chronology Nobody Wants to Own

Novo Holdings completed its acquisition of Catalent, Inc. on February 5, 2024, announcing simultaneously that Novo Nordisk would acquire three of Catalent’s manufacturing sites, including Bloomington. That transaction closed December 18, 2024. Between announcement and close, Catalent was in an ownership transition — a period when compliance oversight at contract manufacturing organizations historically softens. Regulatory inspection preparation competes with acquisition due diligence. Quality management attention fragments. Site personnel watch leadership changes and wonder about their futures. These are not hypotheticals; they are documented patterns in post-merger manufacturing compliance failures.

By the time FDA inspectors walked into Bloomington on June 23, 2025, the Catalent-to-Novo transition had been complete for six months. Scholar Rock, meanwhile, had been treating this facility as part of its regulatory manufacturing strategy. The inspection ran through July 14 and produced an OAI classification. The warning letter followed on November 20, 2025. Scholar Rock’s refiling, removing the facility, came after that. That sequence matters, because it tells you exactly when Scholar Rock learned it had a problem: after the FDA told them in the most formal terms available.

That is not due diligence. That is reactive compliance.

What the Regulatory Record Actually Shows

An OAI classification is not a yellow flag. Under FDA’s inspection classification framework, OAI means the agency has found significant objectionable conditions that warrant regulatory action — the most serious classification available before a consent decree or injunction. For a sponsor relying on that facility to support a BLA under review, an OAI is effectively a manufacturing hold on that component of the application. The FDA’s March 2026 draft guidance, “Responding to FDA Form 483 Observations at the Conclusion of a Drug CGMP Inspection,” makes the remediation pathway clear: sponsors face extended timelines for site qualification when an OAI finding is in play, timelines that can run well past a PDUFA cycle.

Scholar Rock’s decision to refile without the Bloomington facility and proceed with a second fill-finish manufacturer is the operationally sound move. The FDA has accepted the refiled BLA, and the September 30, 2026 PDUFA date is now anchored to that cleaner manufacturing package. But the cost of this pivot is real. Resubmission packages require validation data, comparability studies, and a complete manufacturing section rebuild for the new site. Every week that process consumed is a week apitegromab was not on pharmacy shelves for SMA patients who are already navigating a market where Biogen’s Spinraza, Novartis’s Zolgensma, and Roche’s Evrysdi hold the approved-therapy ground.

The ICER Final Evidence Report on SMA treatments, published September 2, 2025, assessed the comparative clinical evidence for exactly this competitive landscape. Apitegromab’s path to market depends on a differentiated efficacy story. Every month of delay is a month the competitive narrative gets harder to sustain with prescribers and payers.

And the broader damage extends beyond Scholar Rock. Warning Letter 320-26-20 at Bloomington does not just touch one sponsor’s BLA. Any program using that facility as a manufacturing node during the inspection window carries some version of this risk in its regulatory package. Sponsors do not always disclose which contract manufacturers they share with competitors, which means other programs may be carrying Bloomington exposure that has not yet surfaced in a press release or an 8-K.

The Due Diligence Standard That Keeps Failing Sponsors

Here is the counterintuitive read on this situation. The conventional wisdom in clinical operations is that late-stage manufacturing risk is a CMO problem, not a sponsor problem. Sponsors sign quality agreements, conduct periodic audits, and review batch records. If the CMO fails a GMP inspection, the CMO is accountable. That logic is structurally wrong, and the apitegromab situation is the clearest recent proof.

Under 21 CFR Part 211 and ICH Q10, the sponsor bears ultimate accountability for the quality of every product in its BLA, regardless of who physically manufactures it. The FDA does not issue a warning letter to a CMO and then excuse the sponsor. It issues a warning letter to the CMO and then reviews whether the sponsor’s oversight was adequate. Scholar Rock’s manufacturing section in the original BLA relied on a facility that was, at the time of filing, already deep into the compliance deterioration cycle that produced a twenty-one-day inspection and an OAI outcome. The ownership transition from Catalent to Novo Nordisk created an obvious inflection point where an alert sponsor quality team should have escalated audit frequency, demanded updated CAPA documentation, and run scenario planning for what a site substitution would require.

Instead, Scholar Rock learned about the problem from the FDA’s warning letter, not from its own vendor oversight program.

The structural issue here runs deeper than one sponsor’s quality team. Contract manufacturing capacity in biologics and rare disease fills has consolidated significantly over the past five years. The universe of sites capable of handling the fill-finish requirements for a complex biologic like apitegromab is not large. When a facility like Bloomington enters acquisition transition and then OAI, the cascade effect on the sponsors depending on it is disproportionate. Sponsors in rare disease programs, where patient populations are small and commercial timelines are tight, have less margin to absorb a manufacturing site substitution than large-molecule programs with multiple validated sites already in place.

For sponsors running late-stage rare disease programs, the Watchdog directive is specific: build a manufacturing site risk assessment into your BLA strategy at the IND stage, not the pre-BLA stage. Map your CMO’s inspection history, audit cadence, and ownership structure annually. If your fill-finish partner is in an acquisition transition, treat it as a regulatory risk event and activate contingency site validation immediately. Do not wait for an OAI classification to discover you need an alternate manufacturer. By then, the PDUFA clock is already running against you.

For FDA-watchers, the signal to track is whether the agency’s Office of Pharmaceutical Quality begins publishing inspection-cycle data for facilities undergoing ownership transitions as a separate risk category. The Bloomington pattern, a major facility acquisition followed by a compliance deterioration followed by a warning letter that cascades into third-party sponsor programs, is not new. It happened at multiple sites during the post-COVID CMO consolidation wave. A structured early-warning mechanism for acquisition-phase facilities would give sponsors the data they need to make site-substitution decisions before the FDA makes them for you.

The September 30, 2026 PDUFA date for apitegromab is the next hard test. If Scholar Rock’s refiled manufacturing package clears without a Complete Response Letter, it will mean the substitution strategy worked and the timeline held. If it does not, the operational cost of the Bloomington dependency will compound into a second review cycle for a patient population that has already been waiting.

References

1. FierceBiotech — “Scholar Rock ditches Novo’s legacy Catalent plant in FDA refiling of SMA drug”
2. GMP Insiders — “FDA Warning Letter 320-26-20 to Catalent Indiana, LLC, Bloomington, Indiana (November 20, 2025)”
3. Cure SMA — “FDA Accepts Scholar Rock’s BLA to Review Apitegromab for SMA, PDUFA Date September 30, 2026”
4. Novo Holdings — “Novo Holdings Completes Acquisition of Catalent” (December 18, 2024)
5. Arnold & Porter — “FDA Issues Guidance on Responding to FDA Form 483 Observations at the Conclusion of a Drug CGMP Inspection (March 2026)”
6. ICER — “Final Evidence Report on Treatments for Spinal Muscular Atrophy” (September 2, 2025)
7. FDA — “Changes to an Approved NDA or ANDA: Guidance for Industry”