BBIO BBP-418

Limb-girdle muscular dystrophy 2I · BridgeBio · NDA

Of 100 applications in this same position, about 93 get approved.

Until the FDA deadline53d

Base rate76%

Gap+17pts

PDUFA target date 2026-11-27the FDA may act earlier or later

Summary

We put approval in this review cycle at 93%, well above the ~76% base rate for small/mid-cap original NDAs. FORTIFY's 12-month interim analysis showed large, consistent effects: glycosylated alpha-dystroglycan up 1.8x, faster walking (+0.27 m/s, p<0.0001), better lung function (FVC +5%, p=0.007), NSAD +2.6 points and CK down 82%. Safety was clean. According to BridgeBio, after reviewing all the data the FDA recommended traditional rather than accelerated approval. The FDA then granted Priority Review and plans no advisory committee. BBP-418 is a simple oral small molecule. The remaining risks are that the data come from an interim analysis of one trial and that this FDA has issued some unexpected rare-disease CRLs.

Recorded 2026-10-04 19:58 UTC · v1Proof ↓

Evidence · 7 items

Why 93%, not 76%

Indication

Limb-girdle muscular dystrophy type 2I/R9 (LGMD2I/R9), oral; traditional (full) approval sought

76% of comparable applications were approved in the past: the opponent every forecast has to beat. Below are the reasons this forecast differs.

▲ supports approval, ▼ counts against it. More squares, more weight.

01▲ SupportsLarge Randomized Phase 3 data are strong and consistent across biomarker, functional and pulmonary endpoints

FORTIFY randomized 112 patients 2:1 to BBP-418 or placebo; this is the prespecified 12-month interim analysis. The primary interim endpoint, glycosylated alpha-dystroglycan, rose 1.8x from baseline at month 3 (p<0.0001) and stayed up at month 12 (p<0.0001). At 12 months: 100-meter timed test velocity +0.27 m/s vs placebo (p<0.0001), FVC about +5% predicted vs placebo (p=0.0071), NSAD +2.6 points vs placebo (nominal p=0.0001), and serum CK down 82% (p<0.0001). Treated patients improved while placebo patients declined. Results were consistent by genotype, age and baseline FVC.

Source: SEC 8-K 2025-10-27 Ex.99.1; SEC 10-K filed 2026-02-24; NeurologyLive coverage of the MDA 2026 late-breaker
02▲ SupportsMedium The FDA itself recommended pursuing traditional approval after seeing all the FORTIFY data

BridgeBio's January 2026 presentation, filed with an 8-K, says all FORTIFY data including key sensitivity analyses were shown to the FDA. According to the company, the FDA said the data demonstrate consistent treatment effects on multiple efficacy endpoints and recommended orienting the NDA toward traditional approval rather than accelerated approval. This is the company's account, not an FDA document.

Source: SEC 8-K 2026-01-12 Ex.99.1 and Ex.99.2 (J.P. Morgan presentation); 8-K 2026-02-24 Ex.99.1
03▲ SupportsSmall Priority Review granted and no advisory committee planned

The NDA was submitted 2026-03-30 and accepted 2026-05-27 with Priority Review and a PDUFA date of 2026-11-27. The FDA told the company it is not currently planning an advisory committee. The product also holds Fast Track, Orphan and Rare Pediatric Disease designations.

Source: SEC 8-K 2026-05-27 Ex.99.1; SEC 10-Q filed 2026-08-10
04▲ SupportsSmall Clean safety profile for an oral, naturally occurring sugar alcohol

Serious TEAEs were 5.4% on BBP-418 vs 7.9% on placebo; none were treatment-related, there were no deaths and no discontinuations for adverse events. Grade 3 or higher TEAEs were 5.4% vs 5.3%. All diarrhea was grade 1-2 and was less common than on placebo (39.2% vs 52.6%). A REMS is not expected.

Source: BridgeBio/GlobeNewswire press release 2026-03-11 (MDA 2026)
05▲ SupportsSmall Low manufacturing complexity, and the sponsor has already launched a product

BBP-418 is an oral small molecule (ribitol). BridgeBio already supplies Attruby commercially through CMOs. No CMC issues have been disclosed. The specific BBP-418 manufacturers are not named in the filings I read, so site-level inspection risk cannot be assessed.

Source: SEC 10-Q filed 2026-08-10 (reliance on CMOs risk factors)
06▼ AgainstSmall The evidence comes from an interim cut of a single ongoing trial, in a regulatory climate that has produced surprise rare-disease CRLs

Approval rests on the 12-month interim analysis. FORTIFY continues double-blind to 36 months, with NSAD as the final primary endpoint. NSAD significance at 12 months is nominal, and the sample is small (n=112). The FDA in 2025-26 has issued several unexpected CRLs to rare-disease applications, although the agency's own pathway recommendation here offsets much of this.

Source: ClinicalTrials.gov NCT05775848; SEC 10-K filed 2026-02-24
07▲ SupportsSmall Launch preparation is visible

BridgeBio hired an SVP of Sales and Marketing for the BBP-418 launch, says it is poised to launch upon approval, and is running HCP awareness work at MDA Care Centers. R&D spend on BBP-418 rose to $26.7M in Q2 2026. Recent insider sales and a KKR secondary offering are not informative about the FDA decision.

Source: SEC 8-K 2026-02-24 Ex.99.1; SEC 8-K 2026-08-10 Ex.99.1; SEC 10-Q filed 2026-08-10

What would change this forecast

01
A PDUFA extension (major amendment) or disclosure of new FDA information requests: an extension would move the date, and new requests on efficacy would lower the probability
02
Any indication that the FDA wants the 36-month NSAD analysis or more data before approval, or a reversal of its traditional-approval recommendation
03
Disclosure of an inspection problem (Form 483, OAI) at a BBP-418 manufacturing site
04
Company statements about late-cycle meeting outcomes or labeling discussions (positive)

Any change is published as a new version; earlier versions stay exactly as they were.

Confidence

Medium

Manufacturing and inspection risk

Low

The drug is an oral small molecule, a sugar alcohol, from a sponsor that already supplies a commercial product through CMOs. No CMC problems have been disclosed. The specific drug-substance and drug-product sites for BBP-418 are not named in public filings, so inspection-level risk cannot be checked directly.

Record · version 1

Written on 2026-10-04, 54 days before the PDUFA target date.

Timeline

Versions

v1 2026-10-04 19:58 UTC 93% Current version JSON ↓.ots ↓ ○ Timestamp submitted, awaiting block confirmation

Fingerprint

SHA-256f06386d1dc18727176dbe30bef37307fc72cf77ed05b7607a0fd54a14853c750

The fingerprint of the v1 file. It is what the timestamp commits to: change one character of the file and the fingerprint no longer matches.

Verify it yourself

Download the JSON file above and the .ots file of the same name into one folder.
Compute the SHA-256 of the file. It should match the fingerprint above.
Verify with OpenTimestamps. Once the timestamp is in a Bitcoin block, ots verify reports the block time if you run a Bitcoin node; without one, drop both files on the verifier at opentimestamps.org, or run ots info to see the block height and look it up in any block explorer. If the block time is before the FDA’s decision, the file cannot have been written afterwards.

pip install opentimestamps-client
shasum -a 256 v1_20261004T195811Z.json
ots verify v1_20261004T195811Z.json.ots
ots info v1_20261004T195811Z.json.ots

Scoring rule

What is scored is the last version recorded at least 2 days before the PDUFA target date; if the FDA decides early, only versions recorded before the day of its decision count. For this forecast the cutoff is 2026-11-25. Its error (also called the Brier score) is the squared distance between the forecast and the outcome, set against the error of quoting the base rate only.