A first-in-human phase 1 study of LY3866288 (LOXO-435), a potent, highly isoform-selective FGFR3 inhibitor (FGFR3i) in advanced solid tumors with <i>FGFR3</i> alterations: Initial results from FORAGER-1.
Bibliographic record
Abstract
662 Background: Activating alterations in FGFR3 (most commonly S249C) occur in 15-20% of metastatic urothelial cancers (mUC) and <5% in other solid tumors. Erdafitinib, a pan FGFR1-4 inhibitor, improves survival in 2L FGFR3 -altered mUC but has dose limiting toxicities (DLTs) driven by off-target FGFR1/2/4 inhibition. LY3866288 is an oral, potent, isoform-selective, small molecule FGFR3i designed to limit off-target toxicities with preserved activity against acquired FGFR3 resistance mutations. Here we report initial clinical data from the phase 1 dose escalation cohort of LY3866288in FGFR3 -altered advanced solid tumors. Methods: Adults with advanced or metastatic solid tumors with an FGFR3 or FGFR3 ligand alteration (tumor or blood) that progressed on available standard therapies, ECOG PS ≤1, and RECIST v1.1 evaluable (including non-measurable) disease were eligible. Dose escalation used a single-patient accelerated design followed by mTPI-2 method. Key endpoints were safety, PK, and antitumor activity. Serial plasma samples were collected for ctDNA analysis. Results: As of 27 Aug 2024, 101 patients (pts) were treated at 10 dose levels (DLs) of LY3866288 (6 mg QD – 400 mg BID). Median age was 67 (range, 26-93), 69% ECOG PS 1, and 70% had mUC. Median lines of prior therapy was 3 (range, 1-9), including prior FGFRi in 23%. LY3866288 consistently demonstrated trough concentrations that exceeded IC 90 for FGFR3 S249C at DLs ≥200 mg BID. No significant differences in exposures were observed in pts with moderate renal insufficiency (eGFR 30-49 ml/min). No DLT was observed at any DL. At DLs ≥200 mg BID, the most common treatment-emergent AEs (TEAEs) were diarrhea (67%), hyperphosphatemia (28%), fatigue (23%), increased ALT (22%), and AST (22%); most (68%) TEAEs were grade 1/2. TEAEs associated with poor tolerance and compliance to erdafitinib (retinopathy, onycholysis, and hand-foot syndrome) were ≤5% and low grade. Treatment-related AEs (TRAEs) led to dose reduction in 5% of pts and none were associated with discontinuation. In mUC pts with an activating mutation/fusion dosed at ≥200 mg BID, the objective response rate (ORR) was 42% (14/33; 10 confirmed as of 6 Sep 2024, 4 ongoing and pending confirmation); responses were observed in both mutations (Y373C, S249C, R248C, S371C) and fusions (TACC3). In mUC pts previously treated with an FGFRi, the ORR was 45% (5/11). One pt each with NSCLC (S249C) and biliary tract cancer (TACC3) also achieved a PR. 14/16 PRs (88%) are ongoing. Decreases in FGFR3 ctDNA VAF occurred in 12/13 pts (92%) with available results at cycle 2 or 3, of which 8 achieved clearance (5 with PR; 3 with SD). Conclusions: LY3866288 is well-tolerated with robust clinical activity at multiple DLs, including in erdafitinib refractory mUC. Randomized dose optimization is ongoing and updated results will be presented. Clinical trial information: NCT05614739 .
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.002 | 0.003 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".