233 Background: Telisotuzumab adizutecan (ABBV-400) is an antibody drug conjugate (ADC) consisting of a c-Met targeting antibody telisotuzumab conjugated to a potent topoisomerase 1 inhibitor payload adizutecan. The ongoing first in human phase 1 trial (Study M21-404; NCT05029882) shows that ABBV-400 has encouraging radiographic response and ctDNA molecular response (MR) as monotherapy in patients with advanced solid tumors, including mCRC. Herein, correlation between ABBV-400 exposures and % change in ctDNA from baseline and PK/PD analyses using MR are presented for mCRC patients. Impact of c-MET expression and MET amplification ( MET -amp) status on exposures was also evaluated. Methods: Analyses utilized preliminary data in mCRC patients (N=122) from study M21-404 where subjects were treated with ABBV-400 (1.6 – 6.0 mg/kg Q3W). Serial PK samples were collected in cycles 1 (C1) and 3 (C3) and sparse samples across other cycles. C1 exposure metrics (C max , C avg , and C trough ) for both ABBV-400 conjugate and unconjugated payload were obtained by non-compartmental PK analysis. Baseline and C3 day 1 plasma samples were collected and analyzed using the Guardant INFINITY assay for biomarker analysis. ctDNA (circulating tumor fraction [cTF]) was estimated based on 1) variant allele frequency of somatic mutations in a 74 gene panel and 2) methylation signals across targeted regions of the Guardant INFINITY methylation panel. MR was defined as a 50% decrease in cTF from baseline. PK/PD correlations with % change in cTF at C3 and MR at C3 were evaluated. c-Met protein expression was assessed by IHC (VENTANA MET SP44 RxDx Assay) and MET -amp status was based on available local testing results and retrospective ctDNA testing. Results: Higher exposures of ABBV-400 conjugate and payload (primarily C avg for both analytes and C max for conjugate) correlated with greater decrease in % change in cTF at C3 from baseline, as assessed by the 74 gene panel (N =66) or methylation panel (N=74). PK/PD analysis showed that higher exposure was strongly correlated with higher probability of MR (n=66-74, nominal p < 0.05). ABBV-400 conjugate and payload exposures were comparable across c-Met expression H-score (range 9 – 295), cut-offs (≥90% with 1+ intensity, ≥50% with 2+, ≥10% with 3+, ≥25% with 3+, and ≥50% with 3+), and MET -amp status. Conclusions: Exposure-response analyses have previously shown correlation between ABBV-400 conjugate exposures and probability of efficacy (objective response rate) as well as safety in mCRC subjects. The current PK/PD analyses demonstrate that higher ABBV-400 conjugate and payload exposures are also correlated with liquid biopsy data, i.e., ctDNA and MR based on ctDNA. c-MET expression and MET-amp did not have impact on ABBV-400 exposures. Clinical trial information: NCT05029882 .

258 Background: Telisotuzumab adizutecan is an antibody-drug conjugate comprising the c-Met–targeting antibody telisotuzumab conjugated to a topoisomerase 1 inhibitor payload, adizutecan. A phase 1 trial (NCT05029882) in advanced solid tumors reported higher response rates in pts with CRC and high c-Met expression. We present an analysis of responses based on genomic alterations in ctDNA. Methods: Pts with CRC that is refractory to standard treatment were enrolled. Telisotuzumab adizutecan was given IV Q3W. ctDNA was isolated from baseline (BL) and cycle 3, day 1 plasma samples and analyzed with the GuardantINFINITY assay. Circulating tumor fraction (cTF) was estimated on the basis of variant allele frequency of somatic mutations in a 74-gene panel and methylation signals across targeted regions of the GuardantINFINITY methylation panel. Molecular response (MR) was defined as 50% decrease in cTF from BL. Radiographic response (RR) was assessed by RECIST v1.1. Results: Overall, 113 pts had both BL ctDNA and RR data. Confirmed ORR was 18% (20/113). The most prevalent gene alterations included TP53 (75%), APC (68%), and KRAS (66%) mut; PTPRT (56%), ASXL1 (53%), and FLT1 (52%) amp; SMAD4 (44%) and TP53 (43%) deletions; and MET (4%), BRAF , FGFR3, and NRG1 (all 3%) fusions. The Table shows RRs in pts with specific CRC biomarkers, and MR using the 2 panels with corresponding clinical outcomes. RRs were seen in pts with positive plasma samples at BL for TMB, RAS, BRAF, and HER2. MRs were detected in 64% and 65% of pts using the 74-gene and methylation panel, respectively. ORR was higher in pts with MR (35%) than without MR (8%) using the 74-gene, and 35% vs 0% using the methylation panel, respectively. Median PFS (mPFS) was longer in pts with MR. Conclusions: Telisotuzumab adizutecan has promising efficacy. RRs were seen in CRC pts with heterogeneous genomic profiles, including pts positive for actionable biomarkers in the metastatic setting. More pts with MR experienced RRs and benefited from treatment. Clinical trial information: NCT05029882 . Pts with ctDNA and radiographic response data(N=113) Radiographic cPR, n/N (%) 20/113 (18) Genomic alteration TMB a high ( ≥ 20 mut/Mb) KRAS mut KRAS G12C mut BRAF mut b HER2 amp cPR, n/N (%) Pos 11/48 (23) 11/73 (15) 1/5 (20) 4/14 (29) 2/9 (22) Neg 9/51 (18) 9/40 (23) 19/108 (18) 16/99 (16) 18/104 (17) MR, n/N (%) 74-gene panel 42/66 (64) Methylation panel 48/74 (65) ORR, n/N (%) MR pos 15/42 (36) MR neg 2/24 (8) MR pos 17/48 (35) MR neg 0/26 (0) mPFS, mo (95% CI) Events (n/N) 6.1 (5.3, 6.9)28/42 3.5 (2.6, 4.3)21/24 5.9 (5.3, 6.8)31/48 3.5 (2.7, 4.1)23/26 MR in pts with SD, n/N (%) 74-gene panel 27/45 (60) Methylation panel 31/53 (58) mPFS, mo (95% CI)Events (n/N) MR pos 5.3 (4.5, 5.9)21/27 MR neg 3.9 (2.8, 4.3)16/18 MR pos 5.3 (4.5, 5.9)23/31 MR neg 4 (2.8, 4.4)19/22 a 14 pts not evaluable for TMB. Threshold determined by Guardant. b 1 pt had V600E mutation. mo, months; neg, negative; pos, positive.

10562 Background: The MET proto-oncogene encodes the c-Met protein and is associated with promotion of tumor growth, angiogenesis, metastasis, and drug resistance. Our objective was to describe the prevalence of increased corresponding to c-Met protein expression and its associations with demographic and clinical characteristics among patients with metastatic colorectal cancer (mCRC) in a US-based clinicogenomic database. Methods: We conducted a retrospective cohort study of patients diagnosed with mCRC between 2014 and 2023 using the ConcertAI Patient360 electronic health record database with linkage to Caris Life Sciences genomic data. Patients were followed from first-line therapy (index time) until death or end of study follow up (Jan 2024). A 5-fold cross-validated and cross-cohort tested machine learning classifier trained on c-Met protein immunohistochemistry (IHC) labels (defined as 3+, ≥10% staining) was applied to derive prevalence of increased MET gene mRNA expression from whole transcriptome sequencing. Prevalence rate ratios (RR) with 95% confidence intervals (CI) were calculated using modified Poisson regression. Results: From an overall cohort of 1,020 patients with mCRC with a median age of 63 at metastatic diagnosis, 46% were female and 70% were non-Hispanic White, 20% non-Hispanic Black, 1% non-Hispanic Asian, and 5% Hispanic. At mCRC diagnosis, 81% had an ECOG performance status of 0-1 and 71% were diagnosed with de novo metastatic disease. The overall prevalence of increased MET gene mRNA expression corresponding to 3+, ≥10% c-Met IHC staining in the cohort was 35% (95% CI 32-38) and most samples (84%) were collected prior to treatment initiation. Patients with and without increased expression at this cutoff were broadly similar with respect to demographic and clinical characteristics. However, trends suggested that patients with increased expression had greater representation of individuals that were ages ≥75 years, non-Hispanic Black, had body mass index (BMI) <18.5 kg/m2, ECOG of ≥2, colon as primary tumor site and were microsatellite stable. Conclusions: Increased MET gene mRNA expression was observed among 35% of patients with mCRC in our cohort and was correlated with older age, low BMI at metastatic diagnosis, non-Hispanic Black race/ethnicity, poor performance status, colon as primary site, and microsatellite stable tumors. Prevalence RR (95% CI) Prevalence RR (95% CI) Age, years <45 32% REF Race/ethnicity NH White 35% REF 45-54 34% 1.06 (0.75, 1.50) NH Black 40% 1.12 (0.92, 1.36) 55-64 33% 1.03 (0.73, 1.46) ECOG 0 34% REF 65-74 35% 1.07 (0.77, 1.50) 1 35% 1.03 (0.85, 1.24) ≥75 42% 1.30 (0.93, 1.83) ≥2 44% 1.29 (1.00, 1.68) BMI (kg/m 2 ) <18.5 53% 1.47 (1.03, 2.10) Primary site Rectum 29% REF 18.5-24.9 36% REF Colon 37% 1.29 (1.03, 1.62) 25.0-29.9 35% 0.96 (0.78, 1.19) MSS/MSI MSI-H 28% REF ≥30.0 34% 0.94 (0.77, 1.16) MSS 36% 1.28 (0.84, 1.96)

TPS308 Background: Colorectal cancer (CRC) is the third most common cancer. In the metastatic (m) setting, the 5-year relative overall survival is approximately 15%. Conventional treatment comprises fluorouracil (5-FU)–based chemotherapy. Recently, targeted therapies have been studied for specific molecular subtypes. c-Met overexpression frequently occurs in a variety of tumors, including CRC. ABBV-400 is a c-Met–directed antibody-drug conjugate composed of the monoclonal antibody telisotuzumab conjugated to a potent topoisomerase 1 inhibitor payload. Preliminary data from the first-in-human study of ABBV-400 in patients with advanced solid tumors indicate encouraging efficacy of ABBV-400 monotherapy in patients with third-line or later mCRC. This phase 2 randomized study evaluates the safety, efficacy, and optimal dose of ABBV-400 in combination with 5-FU, folinic acid (FA), and bevacizumab (bev) in patients with mCRC with progression after first line (1L) treatment. Methods: Global, open-label, phase 2 randomized controlled study (NCT06107413). Eligible patients (≥18 years) have confirmed unresectable mCRC and measurable disease per RECIST v1.1, are microsatellite stable or mismatch repair proficient, BRAF V600E wild type, and have progression after 1L combination chemotherapy ± an anti-vascular endothelial growth factor or anti-epidermal growth factor receptor antibody. Primary objectives are (a) optimize ABBV-400 dose in combination with 5-FU, FA, and bev; (b) evaluate the efficacy of the combination, using objective response and progression-free survival as dual primary endpoints; (c) evaluate the safety and tolerability of the combination. Approximately 206 patients planned for enrollment in 2 stages: safety lead-in dose escalation (stage 1; n=30) and dose optimization (stage 2; n=176). In stage 1, patients receive escalating doses of ABBV-400 either every 2 weeks (Q2W; 0.8–2.4 mg/kg) or every 4 weeks (Q4W; 1.6–3.0 mg/kg) in combination with Q2W 5-FU (2400 mg/m 2 infusion), FA (200 mg/m 2 ), and bev (5 mg/kg) in 28-day cycles. Dose escalation of ABBV-400 uses a Bayesian optimal interval design, with target toxicity rate of 30%. Dose-limiting toxicities (DLT) are assessed during cycle 1, with ≥6 DLT evaluable patients required to declare a dose safe for the dose-optimization stage. In stage 2, patients are randomized to up to 4 ABBV-400 dose cohorts (2 with Q2W and 2 with Q4W ABBV-400 schedule; all in combination with Q2W 5-FU, FA, and bev) and a comparator cohort (irinotecan [180 mg/m 2 ] + 5-FU [400 mg/m 2 bolus and 2400 mg/m 2 infusion] + FA [200 mg/m 2 ] + bev [5 mg/kg]; all Q2W). Patients are treated until progression, unacceptable toxicity, or other discontinuation criteria are met. Enrollment was initiated in November 2023, with 3 patients enrolled as of January 4, 2024. Clinical trial information: NCT06107413 .

TPS3162 Background: c-Met (MET protein) is commonly overexpressed in a number of tumors, including hepatocellular carcinoma (HCC), pancreatic ductal adenocarcinoma (PDAC), biliary tract cancers (BTC), esophageal squamous cell carcinoma (ESCC), breast cancer (BC), and head and neck squamous cell carcinoma (HNSCC). Patients with c-Met–overexpressing tumors represent an underserved population, with the need for more effective c-Met–targeting therapies to become available. ABBV-400 is an antibody-drug conjugate, consisting of the c-Met–targeting antibody telisotuzumab conjugated to a potent topoisomerase 1 inhibitor payload. Initial results from the ongoing first-in-human study (NCT05029882) of ABBV-400 in patients with advanced solid tumors indicate a tolerable safety profile, with a maximum tolerated dose of 3 mg/kg once every 3 weeks (Q3W), and promising antitumor activity, with an overall response rate of 24.4% (1). Herein, we describe a signal-seeking study evaluating ABBV-400 treatment in patients with select solid tumors. Methods: Multicenter, open-label, phase 1 signal-seeking study(NCT06084481). Eligible patients (≥18 years) have confirmed locally advanced/metastatic disease measurable per RECIST v1.1 and Eastern Cooperative Oncology Group performance status ≤1. Approximately 220 patients are planned for enrollment across 7 cohorts (HCC, n=40; PDAC, n=40; BTC, n=20; ESCC, n=40; triple-negative BC, n=20; hormone receptor-positive/HER2-negative BC, n=20; HNSCC, n=40). The primary objectives are to assess efficacy and safety/tolerability of ABBV-400 in each tumor indication. Secondary objectives include the evaluation of pharmacokinetics (PK) and immunogenicity of ABBV-400. Pharmacodynamic (PD) and biomarker analyses are exploratory endpoints. Patients receive intravenous ABBV-400 at 3 mg/kg Q3W until disease progression, intolerable toxicity, or any other per-protocol discontinuation criteria. c-Met expression will be assessed retrospectively by immunohistochemistry. The maximum treatment duration is 2 years. Tumor assessments are performed at screening and every 6 weeks from the first dose of study drug, with objective response rate as primary efficacy endpoint and duration of response, clinical benefit rate, progression-free survival, and overall survival as secondary efficacy endpoints. Safety evaluations include adverse events monitoring (graded according to the NCI CTCAE, v5.0), physical examinations, vital sign measurements, ECG variables, and clinical laboratory testing. Blood samples for PK, PD, and biomarker analysis are collected at designated time points throughout the study. Enrollment started in November 2023. As of 19 January 2024, 24 patients have been enrolled. 1. Sharma et al. JCO 2023;41[16 suppl]:3015. Clinical trial information: NCT06084481 .

3015 Background: c-Met overexpression is common in non-small cell lung cancer (NSCLC), gastroesophageal adenocarcinoma (GEA), and colorectal cancer (CRC). There is a need for effective therapies that target c-Met–overexpressing tumors, as there are currently no approved options available. The antibody-drug conjugate (ADC) ABBV-400 consists of the c-Met–targeting antibody telisotuzumab conjugated to a potent topoisomerase 1 inhibitor (Top1i) payload. ABBV-400 exhibited sustained antitumor activity in patient-derived xenograft models of c-Met–expressing NSCLC, GEA, and CRC. Herein, we present data from the dose escalation of the first-in-human study of ABBV-400 monotherapy. Methods: A phase 1 dose escalation/expansion study of ABBV-400 has been initiated in patients with advanced solid tumors (NCT05029882). Primary objectives are to evaluate safety, tolerability, and pharmacokinetics (PK) of ABBV-400, to determine the recommended phase 2 dose, and to assess preliminary efficacy. PK will be characterized for the conjugate, total antibody, and free payload. Adults (≥18 years) with an advanced solid tumor that progressed on standard therapies were enrolled during dose escalation, without restrictions on the basis of c-Met overexpression status. Results: As of January 2023, 47 patients had enrolled in dose escalation with a median follow-up of 6.5 months. Median age was 58 years (range, 34–79), 25 (53%) patients were male, and the most common cancer types were CRC (n=21), NSCLC (n=5), and GEA (n=5). The median number of prior treatment lines was 4 (1–13). Most common hematologic adverse events (AEs) were anemia (66%; grade [G]≥3: 38%), neutropenia (62%; G≥3: 43%), thrombocytopenia (43%; G≥3: 26%), and leukopenia (32%; G≥3: 19%). Nausea (60%, all grade 1–2), fatigue (49%; G≥3: 4%), and vomiting (38%, all grade 1–2) were the most frequent non-hematologic AEs. One patient experienced grade 1 interstitial lung disease. Neutropenia and thrombocytopenia were the dose-limiting toxicities (DLTs) and were dose and exposure dependent. Clinical activity was observed with ABBV-400, with an objective response rate of 24.4% (11/45; 95% CI: 12.9, 39.5). All responses were confirmed partial responses (PR). In addition, 23 patients (50.0%) had stable disease (SD) and 7 (15.2%) had progressive disease. Among patients with CRC, 4/21 (19.0%) had a PR and 13/21 (61.9%) had durable SD, with a disease control rate of 81.0% (95% CI: 58.1, 94.6). Outside of CRC, PRs were observed in patients with NSCLC ( EGFR wildtype and mutant), uterine cancer, and acral melanoma. Conclusions: On the basis of DLTs, a maximum tolerated dose of ABBV-400 was identified. At this dose, safety results appear comparable with other Top1i ADCs. Promising antitumor activity was seen with ABBV-400 across tumor types, justifying further evaluation in the ongoing dose expansion in NSCLC, GEA, and CRC. Clinical trial information: NCT05029882 .

Non-small cell lung cancers (NSCLCs), colorectal tumors, and gastric/gastroesophageal junction adenocarcinomas (GEA) frequently overexpress c-Met. The first-generation c-Met targeting antibody-drug conjugate carrying a monomethyl auristatin E payload, telisotuzumab vedotin (ABBV-399), recently received USDA Breakthrough Therapy Designation for nonsquamous, c-Met expressing NSCLC. The next-generation version, ABBV-400 uses a topoisomerase inhibitor payload.

9032 Background: The antibody-drug conjugate telisotuzumab vedotin (Teliso-V) is composed of the c-Met–targeting antibody telisotuzumab (ABT-700) linked to the microtubule inhibitor monomethyl auristatin E. In the LUMINOSITY study (NCT03539536), efficacy of Teliso-V was seen in patients (pts) with EGFR wildtype nonsquamous NSCLC and c-Met overexpression (≥25% tumor cells at 3+ intensity by IHC); overall response rate: 36.5%. Data are limited on whether specific driver oncogene states affect responses. We investigated genomic alterations in relation to response to Teliso-V in this population. Methods: Pts received 1.9 mg/kg Teliso-V monotherapy once every 2 weeks in LUMINOSITY. ctDNA was isolated from plasma collected at different timepoints. The PGDx elio plasma complete assay was used to identify genomic alterations in ctDNA samples. This assay included 521 genes for single nucleotide variants and insertion-deletion mutations, 38 for amplifications (amp), and 21 for translocations. Results: In total, 52 pts were included in the study; ctDNA from 48 pts was analyzed. The overall response rate among pts with ctDNA results was 37.5% (18 pts with partial response) compared with 36.5% for the ITT population of 52 pts. Genomic alterations are listed in the Table.Three out of 4 pts with MET amp at baseline responded, accounting for 17% of total responses. The observed MET amp frequency in this MET IHC preselected cohort was 8%, which is similar to the prevalence observed in tissue analysis by FISH. Of note, 1 nonresponder harbored a MET ex14del mutation at baseline, and a responder had a low-frequency mutation detected at the final visit. Mutations in KRAS were the most common genomic alteration and were detected in 13 (27%) pts at baseline. Three pts with a KRAS mutation were responders; among these, 2 out of 3 had a KRAS G12C mutation (seen in 3 pts total). Response rates were higher in pts with MET amp (75%; 95% CI: 0.30, 0.95) vs those without MET amp (34%; 0.22, 0.49), and higher in pts without KRAS mutations (43%; 0.28, 0.59) vs those with KRAS mutations (23%; 0.08, 0.50); however, confidence intervals were wide and larger sample sizes are needed. Conclusions: MET amp occurred more frequently in responders; however, Teliso-V activity was not restricted to these pts, as most responders were not MET amplified. Specific genomic alterations beyond MET may influence clinical response. The current analysis demonstrated numeric differences between pts with identified drivers who did or did not respond to Teliso-V. Additional research on this topic is needed in larger pt cohorts and/or with tissue-based NGS analyses. [Table: see text]

e21105 Background: Biomarker-targeted antibody-drug conjugates (ADCs) have shown promise in treating lung cancer. Telisotuzumab vedotin (Teliso-V; ABBV-399) is a first-in-class MET (also known as c-Met)-directed ADC comprising the monoclonal antibody telisotuzumab (ABT-700) conjugated to a cytotoxic microtubule inhibitor, monomethyl auristatin E (MMAE), via a cleavable dipeptide linker. In the phase 2 LUMINOSITY study (NCT03539536), Teliso-V demonstrated promising anticancer activity in previously treated patients with MET-overexpressing (OE), non-squamous epidermal growth factor receptor wild type ( EGFR WT) non-small cell lung cancer (NSCLC; 52.2% overall response rate in MET OE high group, 36.5% in all MET OE cohort [intermediate and high]) and an acceptable safety profile (Camidge et al. J Clin Oncol. 2022;40:16 suppl, 9016). These data provide proof of concept that biomarker-selected MMAE-based ADCs could be beneficial to patients with NSCLC. Cofetuzumab pelidotin (ABBV-647), an ADC with a similar composition to Teliso-V, contains an anti-protein tyrosine kinase 7 (PTK7) monoclonal antibody (hu6MO24) conjugated to a microtubule-inhibiting cytotoxin, Aur0101 auristatin, via a cleavable cysteine-reactive linker. PTK7 expression and oncogenic functions have been reported in several cancers. We sought to establish the co-prevalence of MET OE and PTK7 in NSCLC to understand if both these antigens targeted by ADCs are co-expressed or present in distinct tumors. Methods: Antigen prevalence was analyzed in tumor samples from patients at the City of Hope National Medical Center with non-squamous NSCLC and EGFR WT or unknown status. Immunohistochemistry (IHC) assays used were MET (SP44) Assay for MET OE (Roche Tissue Diagnostics; positive if ≥25% cells at 3+ intensity) and an AbbVie-developed assay for PTK7 expression (positive if ≥90% cells at ≥2+ intensity). Results: A total of 148 patients (median age 67 years, 52% stage ≥III at diagnosis, 68% ECOG 0–2) were screened (data shown in table). About 24% of the patients were MET IHC positive, whereas 11% were PTK7 IHC positive. Further, MET OE and PTK7 had complementary prevalence with only 3% of the patients co-expressing both antigens. Conclusions: MET OE and PTK7 expression by IHC were found to be complementary in patients with non-squamous EGFR WT/unknown NSCLC. About 32% of patients were positive for MET OE or PTK7 expression or both. Data represent patients from a single center and more pre-treatment tissue samples that were viable and available. These IHC findings suggest that MET OE and PTK7 are indeed complementary NSCLC biomarkers. [Table: see text]