Parikh, K

TPS3182 Background: MTAP deletion in solid tumors causes intracellular accumulation of methylthioadenosine (MTA) which partially inhibits activity of the key methylating enzyme, protein arginine methyltransferase 5 (PRMT5) and creates synthetic lethal dependencies on PRMT5 and methionine adenosyltransferase 2A (MAT2A), the rate limiting step in the synthesis of PRMT5 substrate, S-adenosyl methionine. PRMT5 and MAT2A are essential to transcription modulation, gene splicing, and DNA damage response. IDE892 is an MTA-cooperative PRMT5 inhibitor designed to exploit this vulnerability in MTAPdel tumors. Preclinical studies report robust antitumor activity with IDE892 monotherapy in MTAPdel xenograft models and an enhanced response when combined with IDE397 (an allosteric MAT2A inhibitor). IDE892-001 is a Phase 1 study evaluating safety, pharmacokinetics (PK), pharmacodynamics (PD), and preliminary antitumor activity of IDE892 alone and in combination with IDE397. Methods: IDE892-001 is an ongoing, open-label, multicenter four-part study: IDE892 monotherapy dose escalation (Part 1), monotherapy dose expansion in MTAPdel NSCLC (Part 2), IDE892 + IDE397 dose escalation (Part 3), and combination expansion in MTAPdel NSCLC (Part 4). Adults with advanced or metastatic MTAPdel solid tumors including lung, urothelial, gastrointestinal cancers (including pancreatic and biliary tract cancers) and mesothelioma are eligible following disease progression on standard therapies. Key exclusion criteria include symptomatic brain metastases, cardiac disease, active severe infection, and prior treatment with a PRMT5 or MAT2A inhibitor. Part 1 uses a Bayesian optimal interval design to determine maximum tolerated dose (MTD) and recommended doses for expansion (RDE). Part 3 uses a modified toxicity probability interval design to evaluate escalating combinations of IDE892 and IDE397. Oral treatment is given QD in 21-day cycles until progression or unacceptable toxicity. Serial blood samples are collected for PD analyses. Imaging will be performed every 6 weeks through week 24, then every 9–12 weeks. Efficacy endpoints will be assessed by RECIST v1.1. Primary objectives for dose-escalation cohorts (Parts 1 and 3) are safety and tolerability, including determination of MTD/RDE. In expansion cohorts (Parts 2 and 4), co-primary objectives include safety and preliminary antitumor activity (objective response rate and duration of response). Secondary endpoints for all parts include PK of IDE892 alone and in combination with IDE397. Exploratory assessments include progression free survival, changes in circulating and tumor-based markers of PRMT5 pathway modulation, molecular predictors of response, exposure–response relationships, and metabolite characterization. Clinical trial information: NCT07277413 .

8094 Background: Patients with extensive-stage small cell lung cancer (ES-SCLC) who progress after platinum-based chemotherapy plus immunotherapy have limited options. Whether adding lurbinectedin while continuing immune checkpoint blockade at relapse improves outcomes is unknown. We report results for the platinum-resistant cohort (progression ≤3 months from last chemotherapy) of MC1923. Methods: MC1923 is a phase II trial using a Simon optimal two-stage design. Patients were assigned to a starting dose of durvalumab 1500 mg IV plus lurbinectedin 3.2 mg/m 2 IV on Day 1 of 21-day cycle. The primary endpoint was the 6-month progression-free survival rate (PFS6). Accrual continued to 22 eligible patients if ≥2/9 achieved PFS6; the regimen would be considered promising if ≥7/22 (32%) were alive and progression-free at 6 months. Secondary endpoints included adverse events (AEs), objective response rate (ORR), progression-free survival (PFS), and overall survival (OS). Results: Twenty-two patients enrolled (02/04/2022–05/21/2025); all were eligible and treated. Median age was 66 years; 32% were male; ECOG performance status was 0 in 9% and 1 in 91%; 96% had prior atezolizumab. Median cycles delivered were 4 (range 1–13). PFS6 was 4/22 (18.2%; 95% CI, 7.5–44.1%), below the prespecified threshold. Median PFS was 3.1 months (95% CI, 1.6–5.3). ORR was 13.6% (3/22; all partial responses; 95% CI, 2.9–34.9%). At data cutoff (12/18/2025), 4 patients were alive; median follow-up was 16.8 months (range 5.5–39.6). Median OS was 7.4 months (95% CI, 4.3–18.6) and 1-year OS was 33.1% (95% CI, 17.6–61.9%). One (1) patient discontinued treatment with durvalumab due to AE. No treatment-related Grade 5 AEs occurred; Grade 3–4 AEs at least possibly related to treatment occurred in 32% (7/22); Grade 4 AEs occurred in 5% (1/22), all hematologic. Most common Grade 3 AEs were decreased neutrophils and white blood cells (each 9%). Conclusions: Durvalumab plus lurbinectedin demonstrated manageable toxicity in platinum-resistant ES-SCLC after chemoimmunotherapy but did not meet the prespecified PFS6 efficacy threshold, supporting the need for alternative strategies in this high-risk population. Clinical trial information: NCT04607954 .

3014 Background: Macrocyclic next-generation tyrosine kinase inhibitors (TKIs) have transformed outcomes in ALK- and ROS1-positive NSCLC; such creatively designed medicines are similarly needed to improve outcomes in EGFR-mutant NSCLC. Using a novel, mutant-selective macrocyclic structure, BH-30643 was designed for super-potency against driver EGFRm, largely sparing wildtype (WT) EGFR, and with unique invulnerability to resistance from C797S with or without T790M. Here we report emerging first-in-human dose-escalation data from the SOLARA trial (NCT06706076). Methods: Phase 1 dose escalation used a BOIN design with backfill at potentially efficacious doses. Expansion cohorts targeted populations of interest. Patients (pts) had advanced NSCLC with EGFR and/or HER2 mutations detected on local testing (tissue or plasma). Measurable disease was required; asymptomatic untreated brain metastases (BM) were permitted. Objectives included safety, PK, and RECIST response rate (ORR). Plasma NGS was performed at baseline and on treatment. Results: As of 01/05/2026, 72 pts enrolled into dose escalation and backfill across 7 dose levels at a total daily dose of 20mg -160mg, median age 62, 44% Asian, 65% with history of BM, median of 3 prior lines of treatment (range 1-12). EGFR mutations included classical (38 pts), exon20ins (14 pts) and other/atypical (18 pts) or HER2 mutations (2 pts). Plasma exposures at doses of 40mg BID and above achieved > 10x coverage over target EC90 and exceeded exposure levels of most contemporary EGFR TKIs. Common TRAE ( > 10%) were WT EGFR-associated, including diarrhea (38%), rash (28%), fatigue (15%), stomatitis (13%), and were predominantly grade 1. Bilirubin elevation was seen in 26 pts (36%) related to off-target UGT1A1 inhibition (Gilbert’s-like). Grade 3 TRAE were seen in 15 pts (18%), most commonly bilirubin (8/15); DLTs included bilirubin increase and mucositis, occurring at doses ≥ 60mg BID. No pneumonitis was observed. Responses were observed across diverse EGFRm subsets, including in CNS. Including expansion pts, 28 pts enrolled with C797S on their most recent informative molecular testing (6 with concurrent MET+ or KRAS+), with 23 still on therapy. Of 17 with on-treatment scans, partial responses (confirmed or ongoing) were seen in 10 (59%); ORR was comparable with (50%) or without (66%) T790M. Of 9 pts with baseline C797S detected in ctDNA (3 with T790M), 7 had > 99% reduction of C797S VAF on treatment. Conclusions: Leveraging a novel macrocyclic scaffold, BH-30643 is the first TKI monotherapy to demonstrate clinical responses against C797S both with or without T790M. High plasma exposures combined with super-potency, CNS activity, and favorable safety offers potential for deep and durable EGFR inhibition. Enrollment into backfill and expansion cohorts is ongoing to better characterize activity in both TKI-naïve and resistant pts. Clinical trial information: NCT06706076 .

Abstract Purpose: Circulating tumor fraction estimate (ctFE) is a machine learning–derived composite metric of circulating tumor DNA (ctDNA) burden. We hypothesized that pre-treatment and early on-treatment ctFE could robustly risk-stratify patients with locally advanced (LA) and oligometastatic non–small cell lung cancer (NSCLC) treated with radiotherapy (RT). Experimental Design: In a prospective phase II clinical trial (NCT03916419), 26 patients with unresectable stage IIB to IIIC NSCLC received magnetic resonance (MR)-guided hypofractionated chemoradiotherapy (chemoRT) followed by immunotherapy. Plasma ctDNA was profiled at baseline and mid-treatment (days 10–14) to derive ctFE and maximum variant allele frequency (Max VAF). A burden-based ctFE threshold derived from baseline samples was applied unchanged to mid-treatment samples and validated in two external cohorts: LA NSCLC treated with chemoRT (LA-RW; n = 94) and oligometastatic NSCLC treated with RT (OM-RW; n = 309). Results: Pre- and mid-treatment ctFE burden strongly stratified overall survival (OS) and progression-free survival (PFS), outperforming Max VAF and ctFE detectability. The baseline ctFE was prognostic for OS (HR 5.93, P = 0.005) and PFS (HR 11.08, P < 0.001) and remained significant at mid-treatment (OS: HR 7.08; PFS: HR 12.06; both P < 0.001). Early ctFE dynamics defined three molecular response groups with OS separation (median OS 60.8 vs. 13.0 vs. 2.9 months; P < 0.001). ctFE remained associated with survival in both validation cohorts. Conclusions: Early ctFE derived from a clinically available, tumor-naïve ctDNA assay enables noninvasive risk stratification in LA and oligometastatic NSCLC treated with RT, supporting its use as a practical biomarker for precision treatment adaptation.

ABSTRACT Introduction Peyronie's Disease (PD) can coexist with erectile dysfunction (ED). International guidelines recommend that management of PD include an assessment of each patient's ability to initiate and sustain erection. PD causes significant stress to the patient and his partner; that distress may limit their ability to assess adequacy of penile rigidity. Further complicating evaluations based on history is the fact that PDE5-Inhibitor use is common. Objective The primary aim of this study is to non-invasively assess vascular erectile integrity in the setting of PD. Methods 1490 patients who underwent intracavernous injection (ICI) followed by Color Doppler Duplex Ultrasound (CDDU) at our institution were retrospectively analyzed. CDDU findings were recorded following injection of low dose alprostadil (10-20 mcg) and again after a period of privacy and visual sexual stimulation. CCDU findings including peak systolic velocities (PSV), and resistive indices (RIs) were recorded. Arterial insufficiency (AI) was defined as either a post-stimulation PSV < 25 cm/sec (severe AI) or a PSV 25-34.9, RI ≥ 0.9(mild AI). Cavernous Venous Occlusion Disease (CVOD) was defined as post-stimulation PSV ≥ 35 cm/sec with RI < 0.9. Mixed was defined as post-stimulation PSV 25-34.9 with RI < 0.9. Vascular normal was defined as post-stim PSV ≥ 35 with RI ≥ 0.9. Results Our cohort of 1490 patients included 900 (60.4%) with a complaint of both PD + ED; 461 (30.9%) with complaint of ED only and 129 (8.7%) with complaint of PD only. Following ICI with PGE1, 310 men were found to have PD and 767 were found to have PD + ED. Patients with a CDDU confirmed diagnosis of PD alone were younger (median: 56.9 vs. 60.8 y, p < 0.001), less likely to have hypertension [103/310 (33.2%) vs. 365/767 (47.6%), p < 0.001], less likely to have used PDE-5 inhibitor [219/310 (70.6%) vs. 616/767 (80.3%), p < 0.001], and less likely to have failed to a PDE-5 inhibitor [142/219 (64.8%) vs. 484/616 (78.6%, p < 0.001]. Diabetes was slightly more common in men with PD + ED compared to PD [270 (35.2%) vs. 94 (30.3%), p = 0.063], but not statistically significant. CDDU diagnoses for men with ED + PD were: AI 262/767 (34.2%), CVOD 305/767 (39.8%), mixed vascular ED 200/767 (26.1%). By definition all men with PD alone were vascular normal. Self-assessments by SHIM scores were abnormal in both groups ED + PD and PD [median(interquartile range): 10 (5 – 17) vs. 14 (8 – 20), p< 0.001]. Conclusions By history alone, patients with ED + PD vs. PD only can't reliably be identified. This is likely related to the distress caused by PD and the tendency to physicians to treat or patients to self-medicate all erectile complaints with PDE5-Inhibitors. For non-invasive treatments distinguishing between ED + PD vs. PD is not critical. Before any patient is triaged to surgical intervention an evidence-based assessment of vascular erectile integrity should be performed. In our cohort of men, Doppler analysis demonstrated that at least 6 out of 10 PD patients have some form of vascular ED. Disclosure No