Brigimadlin (BI 907828) in MDM2-amplified, TP53 wild-type biliary tract, pancreatic, lung, and bladder adenocarcinomas: Strategic Shutdown | Claidex

Q: What happened in NCT05512377?

NCT05512377 was a PHASE2 study of Brigimadlin (BI 907828) in MDM2-amplified, TP53 wild-type biliary tract, pancreatic, lung, and bladder adenocarcinomas sponsored by Boehringer Ingelheim. The trial was terminated or indexed as a failure claim. Boehringer Ingelheim terminated Brightline-2, the Phase 2 of brigimadlin in MDM2-amplified biliary, pancreatic, lung, and bladder tumors. With Brightline-1 already missed and the rest of the program wound down, the MDM2-p53 inhibitor class has eight discontinued programs and two stragglers.

Q: What is the Mechanism Risk Score for MDM2 in MDM2-amplified, TP53 wild-type biliary tract, pancreatic, lung, and bladder adenocarcinomas?

The Claidex Mechanism Risk Score (MRS) for MDM2 in MDM2-amplified, TP53 wild-type biliary tract, pancreatic, lung, and bladder adenocarcinomas is 29/100 (yellow band). This score quantifies the documented clinical failure burden for this target-disease pair based on post-mortems in the Claidex Failure Atlas.

Q: What target does Brigimadlin (BI 907828) act on?

Brigimadlin (BI 907828) targets MDM2. The Open Targets association score for MDM2 in MDM2-amplified, TP53 wild-type biliary tract, pancreatic, lung, and bladder adenocarcinomas is 0.37.

Claidex Editorial Team

doi:10.5281/zenodo.20301169

Brigimadlin and Brightline-2: Boehringer closes a twenty-year MDM2-p53 bet

OncologySponsorMay 17th, 2026·5 min read·10.5281/zenodo.20301169

Boehringer Ingelheim terminated Brightline-2, the Phase 2 of brigimadlin in MDM2-amplified biliary, pancreatic, lung, and bladder tumors. With Brightline-1 already missed and the rest of the program wound down, the MDM2-p53 inhibitor class has eight discontinued programs and two stragglers.

Mechanism Risk Score

Component	Points
Phase-weighted failure burden	10.7 / 40
Archetype severity	2.0 / 25
Temporal recency	4.3 / 15
Genetic evidence deficit	9.4 / 15
Programmatic saturation	2.5 / 5

For MDM2 in MDM2-amplified, TP53 wild-type biliary tract, pancreatic, lung, and bladder adenocarcinomas, the Mechanism Risk Score is 29/100 (yellow band). The score is a failure-burden index derived from Claidex post-mortems on this target–disease pair, not a probability of approval.

MRS 29/100 (YELLOW). 1 programs across MDM2 have been documented for MDM2 in MDM2-amplified, TP53 wild-type biliary tract, pancreatic, lung, and bladder adenocarcinomas: 0 Phase 3, 1 Phase 2, 0 Phase 1 — of which 0 were efficacy failures, 0 safety, 0 biomarker, and 1 operational (enrollment, sponsor, or funding). The most informative failure on file is Brigimadlin and Brightline-2: Boehringer closes a twenty-year MDM2-p53 bet. This score quantifies the documented failure burden; the Open Targets association score of 0.37 reflects weak genetic anchoring, compounding the documented failure record. The MRS is not a prediction of future trial outcomes — it is a structured summary of the empirical record, recomputed live from the Claidex claims table, and intended to flag mechanisms where any new program must explicitly resolve each prior failure mode before pursuit is justified.

This score does not predict whether the next trial will succeed. It flags how heavy the documented mechanistic failure record is before a new program is justified.

What was tried

Brightline-2 was the Phase 2a/2b open-label single-arm trial of brigimadlin (BI 907828), an MDM2-p53 antagonist developed by Boehringer Ingelheim. The trial enrolled 99 patients across four cohorts: locally advanced or metastatic biliary tract adenocarcinoma, pancreatic ductal adenocarcinoma, MDM2-amplified non-small cell lung cancer, and MDM2-amplified urothelial bladder cancer. All patients had MDM2 amplification and wild-type TP53, the biomarker pair that the MDM2 inhibitor class has chased since the first nutlin paper. NCT05512377 terminated on September 25, 2025, with "Sponsor decision" listed in the trial record and the formal results update posted within the last week.

The termination is the second-to-last act of a portfolio-wide shutdown. Boehringer confirmed to ApexOnco in April 2025 that brigimadlin had been removed from the pipeline in all indications. Brightline-1, the Phase 2/3 in first-line dedifferentiated liposarcoma, had already missed its primary endpoint. Brightline-3, the brigimadlin plus ezabenlimab combination, was withdrawn from ClinicalTrials.gov before enrollment.

The biological hypothesis

MDM2 is the canonical negative regulator of p53. It ubiquitinates p53 and shuttles it for proteasomal degradation, keeping nuclear p53 levels low under non-stressed conditions. The therapeutic logic dates to the 1990s. In TP53 wild-type tumors with MDM2 amplification, the wild-type p53 protein is present but kept inert by excess MDM2. A small molecule that occupies the p53-binding pocket on MDM2 should release p53, restore its transcriptional program, and trigger apoptosis or senescence in tumor cells while sparing normal tissue.

Gollner and colleagues at Boehringer described brigimadlin as a high-affinity isoindolinone-derived inhibitor with picomolar p53-MDM2 disruption potency and a pharmacokinetic profile tuned for intermittent dosing, which the group hoped would mitigate the hematologic toxicity that doomed earlier compounds. Preclinically, BI 907828 produced sustained regressions in MDM2-amplified liposarcoma patient-derived xenografts at exposures achievable in humans. The first-in-human Phase Ia readout reported by LoRusso et al. in 2023 showed a 12 percent objective response rate across heavily pretreated solid tumors with disease control above 50 percent. Dedifferentiated liposarcoma, with its near-universal MDM2 amplification, became the lead indication.

What actually happened

Brightline-1 randomized first-line DDLPS patients to brigimadlin or doxorubicin. Brigimadlin numerically beat doxorubicin on confirmed response rate but missed the primary PFS endpoint, with a hazard ratio of 0.79 and p = 0.0956. The result was not enough to displace anthracycline, which has been first-line in advanced soft tissue sarcoma for forty years. Brightline-4, the single-arm Phase 3 confirmatory study, never read out. Brightline-2 was the Phase 2 biomarker-amplification basket designed to find new indications that might rescue the program. The trial closed without results posting, and Boehringer terminated brigimadlin development across all uses.

MDM2-p53 inhibitor programs across two decades. Brigimadlin joins eight discontinued compounds. Sources: NCT05512377, NCT05218499, ApexOnco April 2025, ClinicalTrials.gov.

The class context is the more important data point. Idasanutlin (Roche) failed in the MIRROS Phase 3 in relapsed AML. Milademetan (Rain, then Pathos AI) failed in MANTRA, the DDLPS Phase 3, and showed an exploratory ORR of 7 percent in intimal sarcoma. Siremadlin (Novartis) was discontinued in Phase 1/2. SAR405838 (Sanofi), MK-8242 (Merck KGaA), and ASTX295 (Otsuka) all stopped in Phase 1. Only navtemadlin (Kartos) and alrizomadlin (Ascentage) remain in active development, both pursuing myeloid disease and rare sarcomas rather than common solid tumors.

Failure mechanism, best guess

The class has three recurring problems and they all showed up at once for brigimadlin.

First, MDM2 amplification is necessary but not sufficient. The biomarker selects for tumors that depend on MDM2 to suppress p53, but it does not predict the downstream apoptotic threshold. Many MDM2-amplified tumors carry concurrent CDKN2A/B deletion, MDM4 co-amplification, or downstream apoptotic pathway lesions (BAX loss, BCL2 family imbalance) that blunt p53-driven cell death even when p53 is reactivated. Pellot Ortiz and colleagues catalogued this resistance landscape in glioblastoma, and similar findings are emerging in monocytic AML, where Allen et al. described a CEBPB/IL-1β/TNF-α feedback loop that protects MDM2-amplified leukemic blasts from p53 reactivation.

Second, the therapeutic window is narrow. p53 reactivation in TP53 wild-type bone marrow precursors causes the same apoptosis the drug is designed to deliver to tumors. Every MDM2 inhibitor program has reported dose-limiting thrombocytopenia and neutropenia at exposures near efficacy. Brigimadlin was designed for intermittent dosing partly to manage this, but the pharmacokinetic-pharmacodynamic modeling published in 2026 shows the active-exposure window in glioblastoma xenografts is narrow even with intermittent schedules.

Third, the magnitude of single-agent benefit has consistently been modest. Across the class, ORR in MDM2-amplified solid tumors clusters around 10 to 20 percent and median PFS around 6 to 8 months, similar to standard cytotoxic comparators. There is no single trial where MDM2 inhibition produced a step-function in outcome of the kind kinase inhibitors produced in BRAF or EGFR-driven disease.

What this means for similar programs

The two remaining MDM2 inhibitors, navtemadlin and alrizomadlin, should be read against this backdrop. Navtemadlin's Phase 3 Poiesis in myelofibrosis, combining with ruxolitinib in patients with suboptimal JAK inhibitor response, is the cleanest remaining test of whether MDM2 inhibition adds value to an established backbone. The Boreas Phase 3 in JAK inhibitor-refractory disease already disappointed.

For mutant p53, the picture is no better. PMV Pharma's Y220C reactivator rezatapopt produced a stock-tanking interim, eprenetapopt was discontinued by Aprea, and the field is back to first-in-human studies with JAB-30355 and similar Y220C compounds. Anyone designing a p53-axis program should now budget for combination therapy from the start, treat MDM2 amplification as one of several enrichment criteria rather than the criterion, and plan a clean preclinical comparison against the standard of care in the chosen indication.

Open questions

Does brigimadlin or any MDM2 inhibitor produce a durable benefit when paired with a BCL2 family inhibitor or CDK4/6 inhibitor that backstops the apoptotic threshold?
Is MDM2 amplification ever sufficient as a single biomarker, or does it need to be combined with MDM4 status, CDKN2A status, and downstream apoptotic profiling?
Will targeted protein degradation of MDM2, as pursued by KT-253 (Kymera), avoid the on-target hematologic toxicity that capped exposure for small-molecule inhibitors, or reproduce it?