VNDA imsidolimab

generalized pustular psoriasis · Vanda · BLA

Of 100 applications in this same position, about 70 get approved.

Until the FDA deadline68d

Base rate76%

Gap−6pts

PDUFA target date 2026-12-12the FDA may act earlier or later

Summary

FDA approval of imsidolimab (Quimilza) for generalized pustular psoriasis in this review cycle is put at 70%, below the 76% base rate for first-time applications from smaller companies. The pivotal trial met its primary endpoint: 53% of patients were clear or almost clear at week 4, against 13% on placebo, and in 2022 FDA approved a drug against the same target on one small trial. But each arm had only 15 patients, FDA set a standard review after Vanda asked for priority review, and this is Vanda's first biologic, made by contractors it has not named. No FDA view of the application is public, so confidence is low.

Recorded 2026-10-05 08:21 UTC · v1Proof ↓

Evidence · 11 items

Why 70%, not 76%

Indication

generalized pustular psoriasis (GPP)

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▲ SupportsSmall The pivotal trial met its primary endpoint at both doses

GEMINI-1 randomized 45 adults in a GPP flare 1:1:1 to a single intravenous dose of imsidolimab 750 mg, 300 mg or placebo. At week 4, 8 of 15 patients (53.3%) on each dose were clear or almost clear (GPPPGA 0/1), against 2 of 15 (13.3%) on placebo. The sponsor reported p=0.0131 for 750 mg in 2023; the 2026 publication reports P=0.023 for each dose. The difference posted on ClinicalTrials.gov is about 40 percentage points, with 95% confidence intervals of 8.27 to 70.57 (750 mg) and 8.66 to 71.47 (300 mg).

Source: AnaptysBio press release, 2023-10-09: https://www.sec.gov/Archives/edgar/data/1370053/000137005323000054/anaptysannouncespositive.htm; Smieszek S et al., NEJM Evidence 2026;5(5):EVIDoa2500272: https://pubmed.ncbi.nlm.nih.gov/42047557/; ClinicalTrials.gov NCT05352893 (GEMINI-1), results posted 2026-03-17: https://clinicaltrials.gov/study/NCT05352893
02▼ AgainstMedium The evidence rests on one very small trial, and the result is statistically fragile

Each arm had 15 patients, so the efficacy claim rests on 8 responders against 2. On those counts a two-sided Fisher exact test gives a p-value of about 0.050 and an unstratified chi-square test about 0.020; one more placebo responder would lift the chi-square p-value to about 0.058 (calculated from the posted counts; the pre-specified test was a stratified Cochran-Mantel-Haenszel test). The key secondary endpoint, pustule clearance (PRS 0/1) at week 1, was reached by 6 of 15 patients (40.0%) on 750 mg against 2 of 15 (13.3%) on placebo, and the posted 95% confidence interval for the difference, -3.74 to 57.07, includes zero. The statistical plan posted with the trial tests in a fixed order (750 mg primary, 750 mg key secondary, 300 mg primary, 300 mg key secondary) and stops at the first failure, so the 300 mg results may not count as formally confirmed. The two doses gave the same week-4 response; 10 of 15 placebo patients left the trial early and became eligible for rescue treatment, and the plan counts rescued patients as non-responders; the placebo group was younger (mean age 33.3 years, against 46.8 and 48.7); and 4 of the 45 patients were enrolled in the United States.

Source: ClinicalTrials.gov NCT05352893 (GEMINI-1), results posted 2026-03-17: https://clinicaltrials.gov/study/NCT05352893; GEMINI-1 statistical plan dated 2022-12-09, posted on ClinicalTrials.gov: https://cdn.clinicaltrials.gov/large-docs/93/NCT05352893/SAP_001.pdf; AnaptysBio press release, 2023-10-09: https://www.sec.gov/Archives/edgar/data/1370053/000137005323000054/anaptysannouncespositive.htm
03▲ SupportsMedium FDA has already approved a drug against the same target for GPP flares on one small trial

Spevigo (spesolimab), also an antibody against the IL-36 receptor, was approved on 1 September 2022 for GPP flares on a single placebo-controlled trial of 53 patients (Effisayil-1): at week 1, 19 of 35 patients (54%) on the drug had no visible pustules, against 1 of 18 (6%) on placebo, a difference of 49 percentage points (95% CI 21 to 67). This shows that FDA accepts a single small trial in this disease, and an approved drug with the same mechanism lends biological support to imsidolimab's result. The comparison has limits: spesolimab had breakthrough therapy designation and priority review, more patients on active drug, and a larger effect seen earlier.

Source: FDA Drug Trials Snapshot: Spevigo: https://www.fda.gov/drugs/drug-trials-snapshots/drug-trials-snapshots-spevigo; Boehringer Ingelheim press release, 2021-12-15: https://www.prnewswire.com/news-releases/us-fda-grants-priority-review-for-spesolimab-for-the-treatment-of-flares-in-patients-with-generalized-pustular-psoriasis-gpp-a-rare-life-threatening-skin-disease-301444799.html
04▼ AgainstMedium Vanda's first biologic, and the manufacturer has not been named

Vanda's approved products are all small-molecule drugs made by contract manufacturers; the company has no manufacturing facilities. Imsidolimab is a monoclonal antibody developed by AnaptysBio. Under the January 2025 licence, AnaptysBio's contract-manufacturing agreements, its existing drug supply and a GMP drug-substance batch manufacturing credit passed to Vanda, with a technology transfer planned for 2025. Neither company has publicly named the drug-substance or drug-product sites, so their FDA inspection records cannot be checked, and there is no public statement on whether FDA's pre-licence inspections have taken place. In August 2026 Vanda said commercial supply manufacturing was nearing completion.

Source: Vanda 10-K for FY2025, filed 2026-02-12: https://www.sec.gov/Archives/edgar/data/1347178/000162828026007460/vnda-20251231.htm; Exclusive License Agreement between AnaptysBio and Vanda, 2025-01-31 (sections 3.1.1, 3.1.3, 3.1.5): https://www.sec.gov/Archives/edgar/data/1370053/000137005325000046/vandalicenseagreement-re.htm; Vanda and AnaptysBio press release, 2025-02-03: https://www.sec.gov/Archives/edgar/data/1370053/000137005325000002/anab-pressrelease2025x01.htm; Vanda 8-K exhibit 99.1, 2026-08-05: https://www.sec.gov/Archives/edgar/data/1347178/000162828026053308/vnda8-k852026exhibit991.htm
05▼ AgainstSmall FDA set a standard review after the company asked for priority review

When it submitted the application in December 2025, Vanda said it had requested priority review, which could have brought approval as early as mid-2026. The goal date FDA set, 12 December 2026, is about twelve months after submission. That matches the standard clock for a new biologic (ten months after the 60-day filing period), not the priority clock (six months). Imsidolimab has orphan drug designation (granted July 2020); there is no public record of breakthrough therapy or fast track designation. A standard review does not by itself make approval less likely, but it suggests FDA did not see a clear advance over the approved IL-36 receptor antibody.

Source: Vanda press release, 2025-12-15: https://www.prnewswire.com/news-releases/vanda-announces-submission-of-biologics-license-application-to-the-fda-for-imsidolimab-for-the-treatment-of-generalized-pustular-psoriasis-302641858.html; Vanda press release, 2026-02-25: https://www.prnewswire.com/news-releases/vanda-pharmaceuticals-announces-fda-acceptance-of-biologics-license-application-filing-for-imsidolimab-for-the-treatment-of-generalized-pustular-psoriasis-302696991.html; PDUFA Reauthorization Performance Goals and Procedures FY2023-2027 (sections I.A.1 and I.B): https://www.fda.gov/media/151712/download; AnaptysBio 10-K for FY2023, filed 2024-03-11: https://www.sec.gov/Archives/edgar/data/1370053/000137005324000011/anab-20231231.htm
06▲ SupportsSmall Re-randomized maintenance data point the same way

In GEMINI-2, 16 patients who had responded in GEMINI-1 were re-randomized to monthly subcutaneous imsidolimab 200 mg or placebo. None of the 8 on imsidolimab flared and all kept a clear or almost clear score; of the 8 on placebo, 63% flared and 25% kept their response. The registry reports a log-rank p=0.0018 for time to first flare and, at week 24, a difference of 36.8 percentage points in patients with no flare (95% CI 2.9 to 70.6; p=0.0334). The numbers are very small, and the trial's primary objective was safety.

Source: AnaptysBio press release, 2024-05-09: https://www.globenewswire.com/news-release/2024/05/09/2879216/0/en/Anaptys-Announces-Positive-Top-Line-GEMINI-2-Phase-3-Clinical-Trial-Results-of-Imsidolimab-IL-36R-in-Generalized-Pustular-Psoriasis-GPP.html; ClinicalTrials.gov NCT05366855 (GEMINI-2), results posted 2026-03-27: https://clinicaltrials.gov/study/NCT05366855; GEMINI-1 and GEMINI-2 poster, EADV 2024: https://www.anaptysbio.com/wp-content/uploads/1058_EADV2024_Reich_Imsidolimab-Ph3_Final.pdf
07▲ SupportsSmall No safety signal in the trials reported so far

In GEMINI-1 none of the 30 patients given imsidolimab had a serious adverse event; the one serious event (sepsis) was on placebo, and there were no deaths. The sponsor reported no infusion reactions and no cases of DRESS or Guillain-Barre syndrome, and 1 of 30 treated patients developed anti-drug antibodies. In GEMINI-2, with follow-up of up to 116 weeks, serious events were reported in 4 patients on open-label imsidolimab (nephrogenic anaemia, raised creatine phosphokinase, bacterial arthritis, pustular psoriasis); according to the publication none led to stopping treatment. The safety database in GPP is small: about 39 patients received the intravenous dose across the two trials.

Source: ClinicalTrials.gov NCT05352893 (GEMINI-1), results posted 2026-03-17: https://clinicaltrials.gov/study/NCT05352893; ClinicalTrials.gov NCT05366855 (GEMINI-2), results posted 2026-03-27: https://clinicaltrials.gov/study/NCT05366855; AnaptysBio press release, 2023-10-09: https://www.sec.gov/Archives/edgar/data/1370053/000137005323000054/anaptysannouncespositive.htm; Smieszek S et al., NEJM Evidence 2026;5(5):EVIDoa2500272: https://pubmed.ncbi.nlm.nih.gov/42047557/; GEMINI-1 and GEMINI-2 poster, EADV 2024: https://www.anaptysbio.com/wp-content/uploads/1058_EADV2024_Reich_Imsidolimab-Ph3_Final.pdf
08▼ AgainstSmall No public record that FDA agreed the trial design in advance

AnaptysBio's annual report for 2023 said it had had only limited discussions with FDA about the design of its later-stage studies, and that FDA might ask for additional trials even though the company believed GEMINI-1 and GEMINI-2 would be sufficient. In February 2025 its chief executive described a pre-BLA meeting with FDA in 2024 as productive, without giving details. No special protocol assessment or other written FDA position has been disclosed.

Source: AnaptysBio 10-K for FY2023, filed 2024-03-11: https://www.sec.gov/Archives/edgar/data/1370053/000137005324000011/anab-20231231.htm; Vanda and AnaptysBio press release, 2025-02-03: https://www.sec.gov/Archives/edgar/data/1370053/000137005325000002/anab-pressrelease2025x01.htm
09▲ SupportsSmall The application was filed without disclosed problems, and no advisory committee is scheduled

FDA accepted the application for filing in February 2026. Vanda described it as under review, with the 12 December 2026 goal date, in its quarterly report of 6 August 2026 and in a release of 24 August 2026, and AnaptysBio repeated the date in a filing of 21 September 2026. Vanda's latest release, of 2 October 2026 on conference posters, does not mention the review. As of 5 October 2026, the only 2026 meeting notice for FDA's Dermatologic and Ophthalmic Drugs Advisory Committee, for 30 October 2026, concerns a different product. Neither company has disclosed a review issue or a change to the goal date.

Source: Vanda press release, 2026-02-25: https://www.prnewswire.com/news-releases/vanda-pharmaceuticals-announces-fda-acceptance-of-biologics-license-application-filing-for-imsidolimab-for-the-treatment-of-generalized-pustular-psoriasis-302696991.html; Vanda 10-Q for Q2 2026, filed 2026-08-06: https://www.sec.gov/Archives/edgar/data/1347178/000162828026053855/vnda-20260630.htm; Vanda press release, 2026-08-24: https://www.prnewswire.com/news-releases/vanda-pharmaceuticals-granted-orphan-designation-for-imsidolimab-for-the-treatment-of-generalized-pustular-psoriasis-by-the-european-commission-302857847.html; AnaptysBio 10-KT, filed 2026-09-21: https://www.sec.gov/Archives/edgar/data/1370053/000119312526396696/anab-20260630.htm; Vanda press release, 2026-10-02: https://www.biospace.com/press-releases/vanda-pharmaceuticals-announces-presentation-at-2026-eadv-annual-meeting; Federal Register notice, 2026-09-25 (advisory committee meeting of 2026-10-30): https://www.federalregister.gov/documents/2026/09/25/2026-19700/dermatologic-and-ophthalmic-drugs-advisory-committee-notice-of-meeting-establishment-of-a-public; FDA advisory committee calendar, meeting of 2026-10-30: https://www.fda.gov/advisory-committees/advisory-committee-calendar/october-30-2026-dermatologic-and-ophthalmic-drugs-advisory-committee-meeting-announcement-10302026
10▲ SupportsSmall The sponsor has two recent first-cycle approvals and is preparing to launch

FDA approved Vanda's Nereus (tradipitant) for motion-induced vomiting on its goal date, 30 December 2025, and Bysanti (milsaperidone) on 20 February 2026, one day before its goal date. Vanda says it has been manufacturing commercial supplies of imsidolimab and now uses the brand name Quimilza. It reported $170.0 million in cash at 30 June 2026, which it expects to fund operations through at least the end of 2027, so its financing does not hinge on this decision.

Source: Vanda 8-K exhibit 99.1, 2025-12-30: https://www.sec.gov/Archives/edgar/data/1347178/000162828025059155/vnda8-k12302025exhibit991.htm; Vanda 8-K exhibit 99.1, 2026-02-20: https://www.sec.gov/Archives/edgar/data/1347178/000162828026010376/vnda8-k2232026exhibit991.htm; Vanda 8-K exhibit 99.1, 2025-05-07: https://www.sec.gov/Archives/edgar/data/1347178/000162828025023154/vnda8-k572025exhibit991.htm; Vanda 8-K exhibit 99.1, 2026-08-05: https://www.sec.gov/Archives/edgar/data/1347178/000162828026053308/vnda8-k852026exhibit991.htm
11▼ AgainstSmall A history of rejections and open disputes with FDA

FDA issued complete response letters for Vanda's tradipitant in gastroparesis (18 September 2024) and Hetlioz in insomnia (4 March 2024). In January 2026 CDER again concluded that Hetlioz for jet lag could not be approved; a formal hearing on that application is scheduled to begin on 14 December 2026, two days after the imsidolimab goal date. Vanda is also in court against FDA over, among other things, the agency's use of review clocks longer than 180 days. These cases involve other drugs and other review divisions, and turned on efficacy evidence that FDA judged insufficient. They show that FDA has turned Vanda down when it found the evidence thin, and that the two sides remain adversaries in several proceedings.

Source: Vanda press release, 2024-09-19: https://www.prnewswire.com/news-releases/fda-declines-to-approve-vandas-marketing-application-for-tradipitant-in-gastroparesis-302253040.html; Vanda 10-K for FY2025, filed 2026-02-12: https://www.sec.gov/Archives/edgar/data/1347178/000162828026007460/vnda-20251231.htm; Vanda 8-K exhibit 99.1, 2026-01-08: https://www.sec.gov/Archives/edgar/data/1347178/000162828026001273/vnda8-k172026exhibit991.htm; Vanda 10-Q for Q2 2026, filed 2026-08-06: https://www.sec.gov/Archives/edgar/data/1347178/000162828026053855/vnda-20260630.htm; Vanda 8-K exhibit 99.1, 2025-10-01: https://www.sec.gov/Archives/edgar/data/1347178/000162828025043489/vnda8-k1012025exhibit991.htm

What would change this forecast

01
Up: Vanda discloses label negotiations or post-marketing commitments with FDA, or says the pre-licence inspections of the manufacturing sites are complete without significant findings.
02
Up: the manufacturing sites are named and have clean recent FDA inspection records.
03
Down: a Form 483 with significant observations, a warning letter or a failed inspection is disclosed for a site that makes imsidolimab.
04
Down: FDA asks for additional clinical data or a second trial, or convenes an advisory committee.
05
Down: FDA extends the goal date after a major amendment (historically not strongly negative, but a sign of open questions), or Vanda's quarterly reports soften the launch wording or stop repeating the 12 December 2026 goal date.
06
Void rather than no: Vanda withdraws the application before FDA acts.

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

Confidence

Low

Manufacturing and inspection risk

Medium

Imsidolimab would be Vanda's first biologic. Vanda has no manufacturing facilities and relies entirely on contract manufacturers; the antibody was developed by AnaptysBio, whose contract-manufacturing agreements, existing supply and manufacturing know-how were transferred to Vanda under the January 2025 licence. The drug-substance and drug-product sites have not been named publicly, so they cannot be checked for FDA Form 483 observations, warning letters or inspection classifications, and there is no public word on FDA's pre-licence inspections. Vanda said in August 2026 that commercial supply manufacturing was nearing completion. A first biologic made by undisclosed contractors after a technology transfer leaves real room for a manufacturing or inspection finding. The rating is a judgement made without knowing the sites; it cannot be made more precise from public information.

Record · version 1

Written on 2026-10-05, 68 days before the PDUFA target date.

Timeline

Versions

v1 2026-10-05 08:21 UTC 70% Current version JSON ↓.ots ↓ ○ Timestamp submitted, awaiting block confirmation

Fingerprint

SHA-256b98d91726a6a1877be9a54e3c17a3bc17a37b8b522ce852f0b7d6c2b3ce76d32

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_20261005T082132Z.json
ots verify v1_20261005T082132Z.json.ots
ots info v1_20261005T082132Z.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 2026-12-10. 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.