Sohn, Joohyuk

1005 Background: In the phase 3 HER2CLIMB-05 study (NCT05132582), TUC + maintenance HP demonstrated a statistically significant improvement in progression-free survival (PFS) vs control treatment (Tx) (hazard ratio: 0.641, P < 0.0001) in patients (pts) with HER2+ locally advanced or metastatic breast cancer (MBC). Here we report additional efficacy and safety outcomes by stratified subgroups. Methods: Pts with centrally confirmed HER2+ MBC without evidence of progression following chemotherapy-based induction Tx (taxane + HP) were randomly assigned 1:1 to TUC (300 mg) or PBO BID + HP. Randomization was stratified by diagnosis ( de novo /recurrent), hormone receptor (HR) status (positive/negative), and presence or history of brain metastases (BM; yes/no). Endocrine therapy (ET) is permitted for pts with HR+ disease. The primary endpoint is investigator-assessed PFS. Confirmed objective response rate (cORR), duration of response (DOR), and safety were evaluated in stratified subgroups. Results: Among pts assigned to TUC + HP (n = 326) or PBO + HP (n = 328), ∼69% had de novo MBC, ∼53% had HR+ status with ∼45% having received concurrent ET, and ∼12% had baseline BM. At data cutoff (Sep 5, 2025), median PFS was longer with TUC than PBO + HP in all stratified subgroups; TUC + HP consistently improved cORR vs PBO + HP (Table). Safety outcomes in subgroups aligned with the overall population. Conclusions: TUC + HP demonstrated clinically meaningful efficacy vs PBO + HP in pts with de novo or recurrent disease, HR+ or HR− disease, and baseline BM or not, with no new safety signals identified. Results were consistent with the overall population and support TUC + HP as a potential new maintenance therapy across pts with HER2+ MBC. Clinical trial information: NCT05132582 . Efficacy outcomes. Overall De novo Recurrent HR+ (± ET) † HR− BM (yes) BM (no) TUC+HP(n=326) PBO+HP(n=328) TUC+HP(n=227) PBO+HP(n=226) TUC+HP(n=99) PBO+HP(n=102) TUC+HP(n=168) PBO+HP(n=176) TUC+HP(n=158) PBO+HP(n=152) TUC+HP(n=41) PBO+HP(n=40) TUC+HP(n=285) PBO+HP(n=288) Median PFS, mos (95% CI) 24.9(21.3−NE) 16.3(12.6−18.7) 28.9(22.7−NE) 16.8(12.9−19.2) 21.3(15.6−27.2) 12.7(8.3−18.1) 25.0(16.5−NE) 18.1(13.0−20.8) 24.9(19.4−NE) 12.6(9.4−16.8) 8.5(4.2−16.5) 4.2(2.2−8.1) 27.2(24.3−NE) 18.1(14.8−20.7) cORR*, % (95% CI) 22.6(18.0−27.8) 15.2(11.3−19.7) 26.1(20.2−32.7) 18.5(13.5−24.4) 15.1(8.5−24.0) 7.0(2.6−14.6) 20.1(14.0−27.5) 12.9(8.2−19.0) 25.2(18.4−33.0) 17.9(11.8−25.5) 15.0(5.7−29.8) 8.3(1.8−22.5) 23.8(18.7−29.5) 16.1(11.9−12.1) Median DOR*, mos (95% CI) 20.9(16.4−NE) 16.9(12.3−NE) NR(16.4−NE) 16.3(10.4−NE) 17.9(8.3−NE) NR(7.2−NE) 20.9(12.6−NE) 18.7(7.8−NE) NR(8.6−NE) 14.5(10.4−NE) 12.6(8.1−NE) 16.3(12.5−NE) 20.9(16.4−NE) 18.7(10.4−NE) *ORR and DOR were assessed in patients with target or non-target lesions at baseline. † Data on HR+ w/ ET will be presented.

1042 Background: The primary analysis of the phase 3 HER2CLIMB-05 study (NCT05132582) showed the addition of TUC to 1L maintenance HP yielded a statistically significant improvement in progression-free survival (per investigator) versus control treatment (hazard ratio: 0.641, P < 0.0001) in patients with HER2+ MBC. Here we report our findings from an in-depth safety analysis of HER2CLIMB-05. Methods: Patients with centrally confirmed HER2+ MBC without evidence of progression following chemotherapy-based induction treatment (taxane + HP) were randomly assigned 1:1 to TUC (300 mg) or placebo (PBO) BID, both in combination with HP. The safety analysis set included all randomly assigned patients who received ≥1 dose of any study treatment. Treatment-emergent adverse events (TEAEs), laboratory values, and TUC/PBO dose modifications and discontinuations were examined. Results: Among patients in the safety analysis set (TUC arm = 326; PBO arm = 324), median treatment durations of TUC and PBO were 17.1 months (range: 0.4–36.5) and 15.5 months (range: 0.5–41.3), respectively. Grade (G) ≥3 TEAEs occurred in 42.3% of patients in the TUC arm and 24.4% in the PBO arm; the most frequent G ≥3 TEAEs in the TUC arm were elevated alanine aminotransferase (ALT; 13.5%) and aspartate aminotransferase (AST; 7.1%). TUC was discontinued in 13.5% of patients due to a TEAE. Cardiac TEAEs were similar between TUC and PBO arms (4.3% vs 6.2%). TEAEs of hepatic events (43.6% vs 15.7%) and diarrhea (72.7% vs 51.2%) occurred at higher incidence in the TUC arm versus the PBO arm (Table). In the TUC arm, increased ALT (28.2%) and AST (25.8%) accounted for the majority of hepatic TEAEs. Most hepatic and diarrhea TEAEs were managed with TUC dose modifications and/or discontinuation; 7.7% of patients discontinued TUC due to hepatic TEAEs and 1.5% discontinued due to diarrhea (Table). Among the patients with a TEAE of diarrhea, 57.7% and 29.9%, respectively, in the TUC and PBO arms used antidiarrheals; the most used medication was loperamide. Further details of the in-depth safety analysis will be presented. Conclusions: TUC addition to 1L HP maintenance therapy may be an effective option for HER2+ MBC with a clinically manageable safety profile. Clinical trial information: NCT05132582 . TEAEs* Any Any hepatic Increased ALT/AST Diarrhea Arm TUC PBO TUC PBO TUC PBO TUC PBO Any G, % 99.1 96.6 43.6 15.7 28.2/25.8 7.1/9.0 72.7 51.2 G ≥3 42.3 24.4 18.1 1.2 13.5/7.1 0.6/0.6 6.1 4.0 Any G: Median time to onset (days) 34.5 85.0 11.0 32.0 Median time to resolution (days) 25.0 22.0 2.0 5.0 Any G: TUC/PBO dose hold, % 49.4 25.3 19.3 2.5 12.6/4.0 0.6/0.6 8.6 3.4 TUC/PBO dose reduction, % 29.1 11.1 16.3 0.9 11.7/2.8 0.3/0.6 6.4 3.1 TUC/PBO discontinuation, % 13.5 2.2 7.7 0 4.0/0.3 0/0 1.5 0.9 *As of data cutoff, Sep 5, 2025.

PURPOSE The HER2CLIMB-05 study (ClinicalTrials.gov identifier: NCT05132582 ) is investigating the efficacy and safety of adding tucatinib to trastuzumab and pertuzumab as first-line (1L) maintenance therapy in patients with human epidermal growth factor receptor 2–positive (HER2+) metastatic breast cancer (MBC). METHODS Patients with centrally confirmed HER2+ MBC without evidence of progression post induction therapy and no or asymptomatic brain metastases (BM) were enrolled. Patients were randomly assigned 1:1 to tucatinib (300 mg) or placebo twice a day combined with trastuzumab/pertuzumab. The primary end point is investigator-assessed progression-free survival (PFS); secondary end points include overall survival (OS), PFS per blinded independent central review, CNS-PFS, and safety. RESULTS Between March 2022 and July 2024, 654 patients were randomly assigned to tucatinib (n = 326) and placebo (n = 328) arms. All patients were female (median age, 54 years), 69.3% had de novo MBC, 52.6% were hormone receptor–positive, and 12.4% had presence/history of baseline BM. In this primary analysis, PFS was statistically significantly improved with addition of tucatinib versus placebo (hazard ratio, 0.641 [95% CI, 0.514 to 0.799]; P < .0001; median PFS: 24.9 v 16.3 months); a PFS benefit was seen regardless of the presence/absence of BM or hormone receptor status. OS data remain immature. The most common treatment-emergent adverse events (TEAEs) in the tucatinib arm were diarrhea (72.7%), nausea (33.1%), and elevated liver enzymes (ALT: 28.2%; AST: 25.8%), of which 6.1%, 0.9%, 13.5%, and 7.1%, respectively, were grade ≥3. In the tucatinib arm, 13.5% discontinued tucatinib because of TEAEs. CONCLUSION Tucatinib addition to trastuzumab and pertuzumab demonstrated improvement in PFS with no new safety signals identified and may be an option for 1L maintenance therapy in patients with HER2+ MBC.

PURPOSE Imlunestrant is a next-generation oral selective estrogen receptor (ER) degrader designed to deliver continuous ER target inhibition, including in ESR1- mutant breast cancer. This phase Ia/b trial determined the recommended phase II dose (RP2D), safety, pharmacokinetics, and efficacy of imlunestrant, as monotherapy and in combination with targeted therapy, in ER-positive (ER+) advanced breast cancer (ABC) and endometrial endometrioid cancer. The ER+/human epidermal growth factor receptor 2–negative (HER2–) ABC experience is reported here. METHODS An i3+3 dose-escalation design was used, followed by dose expansions of imlunestrant as monotherapy or in combination with abemaciclib with or without aromatase inhibitor (AI), everolimus, or alpelisib. Imlunestrant was administered orally once daily and with the combination partner per label. RESULTS Overall, 262 patients with ER+/HER2– ABC were treated (phase Ia, n = 74; phase Ib, n = 188). Among patients who received imlunestrant monotherapy (n = 114), no dose-limiting toxicities or discontinuations occurred. At the RP2D (400 mg once daily), patients (n = 51) reported grade 1-2 nausea (39.2%), fatigue (39.2%), and diarrhea (29.4%). Patients at RP2D had received previous cyclin-dependent kinase 4/6 inhibitor (CDK4/6i; 92.2%), fulvestrant (41.2%), and chemotherapy (29.4%) for ABC and achieved a median progression-free survival (mPFS) of 7.2 months (95% CI, 3.7 to 8.3). Among patients who received imlunestrant + abemaciclib (n = 42) and imlunestrant + abemaciclib + AI (n = 43), most (69.4%) were treatment-naïve for ABC; all were CDK4/6i-naïve. Patients treated with imlunestrant + everolimus (n = 42)/alpelisib (n = 21) had received previous CDK4/6i (100%), fulvestrant (34.9%), and chemotherapy (17.5%) for ABC. No new safety signals or interactions with partnered drugs were observed. The mPFS was 19.2 months (95% CI, 13.8 to not available) for imlunestrant + abemaciclib and was not reached for imlunestrant + abemaciclib + AI. The mPFS with imlunestrant + everolimus/alpelisib was 15.9 months (95% CI, 11.3 to 19.1)/9.2 months (95% CI, 3.7 to 11.1). Antitumor activity was evident regardless of ESR1 mutation status. CONCLUSION Imlunestrant, as monotherapy or in combination with targeted therapy, had a manageable safety profile with evidence of preliminary antitumor activity in ER+/HER2– ABC.

3078 Background: Q901 is a potent, covalently binding CDK7 inhibitor with excellent specificity for CDK7 against other protein kinases. Transcriptional regulation by CDK7 inhibition in cancer cells leads to DNA damage repair response inhibition and increased genomic instability. Q901 also regulates cell cycle checkpoints by inhibiting T-loop phosphorylation and transcriptionally downregulating CDK1, 2 and 4. In preclinical in vivo models, intravenous (iv) administration of Q901 once a week and once every three-week dosing regimen was well tolerated and showed significant antitumor activity. The safety profile, pharmacokinetics (PK), pharmacodynamics (PD) and efficacy data for 18, 36 and 60 mg/m2 are presented. Methods: QRNT-009 (NCT05394103) is an ongoing Phase 1/2 multicenter, open-label, dose escalation and expansion study. Q901 is administered iv once weekly for four weeks, then once every two weeks thereafter in patients with advanced or metastatic ovarian cancer, castration-resistant prostate cancer (CRPC), breast cancer, endometrial cancer, colorectal cancer, small cell lung cancer (SCLC), or pancreatic cancers. Results: As of data cutoff (12Jan2024), 17 patients received Q901 across 3 dose levels: 5 patients at 18 mg/m2, 4 patients at 36 mg/m2, and 8 patients at 60 mg/m2. The median prior lines of systemic therapy were 4 (range 2 - 17). Of 17 patients who received Q901 across all doses, there were no treatment related SAEs, treatment discontinuations, or dose reductions. Most common TRAEs ≥ 15% were nausea (29.4%), anemia (23.6%) and fatigue (23.5%). As of data cutoff, no DLTs were observed. All plasma PK analyses across dose levels showed dose dependent increase of AUC0-last and Cmax. No major metabolite was observed. POLR2A, which is a CDK7 target engagement marker showed biologically effective change starting from 18 mg/m2. 1 patient with pancreatic cancer who received 18 mg/m2 had a partial response with CA19-9 reduction from 4,632 to 219. 2 patients at 18 mg/m2 and 2 patients at 36 mg/m2 had stable disease. Additional safety and efficacy data will be presented. Conclusions: Preliminary data from QRNT-009 study showed that selective CDK7 inhibitor Q901 is well tolerated. Preliminary antitumor activity and pharmacodynamic observations are encouraging. Dose escalation is ongoing to identify MTD or recommended dose for further studies. Clinical trial information: NCT05394103 .

5589 Background: Imlunestrant is a next-generation oral SERD designed to deliver continuous estrogen receptor (ER) target inhibition aimed to improve outcomes for patients (pts) with ER+ cancers. In the first-in-human Phase 1a/1b EMBER trial (NCT04188548), imlunestrant showed favorable safety, pharmacokinetics, and clinical benefit in pre-treated pts with ER+ advanced breast cancer or EEC. Here, we report updated imlunestrant monotherapy data and the first clinical data of imlunestrant + abemaciclib in ER+ EEC pts from EMBER. Methods: Eligible pts had ER+ EEC previously treated with (or deemed inappropriate for) platinum-containing chemotherapy. Prior fulvestrant or aromatase inhibitor therapy was not allowed. In Phase 1a, pts received imlunestrant alone, and in Phase 1b, pts were randomized (1:1) to imlunestrant alone or with abemaciclib. Plasma samples were collected at baseline (all pts) and at cycle 2 (monotherapy pts) for ctDNA analysis (Guardant 360 assay) to correlate with clinical benefit. Primary endpoints were RP2D of imlunestrant monotherapy and in combination. Secondary endpoints included safety, tolerability, and overall response rate (ORR), clinical benefit rate (CBR: complete or partial response, or stable disease ≥24 weeks), and progression-free survival (PFS) using RECIST v1.1. Results: Overall, 72 pts were treated; 39 pts received monotherapy (33 at 400mg [RP2D] and 6 at 800mg po daily) and 33 pts received imlunestrant (29 at 400mg and 4 at 800mg po daily) + abemaciclib (150mg po twice daily). Baseline characteristics, safety, and preliminary efficacy are presented (Table). For monotherapy, the most common TEAEs (all grade/grade 3) were nausea (36%/3%), diarrhea (26%/0), urinary tract infection (26%/3%), and abdominal pain (21%/8%). For imlunestrant + abemaciclib, the most common TEAEs (all grade/grade 3) were diarrhea (88%/3%), nausea (67%/0), fatigue (49%/9%) and anemia (46%/12%). In the monotherapy arm, pts with deeper (≥ 50%) declines in ctDNA variant allele frequency had a higher CBR (4/7 vs 4/17). Conclusions: Imlunestrant, as monotherapy or with abemaciclib, appears safe and tolerable with preliminary evidence of efficacy in pts with metastatic ER+ EEC. Clinical trial information: NCT04188548 . [Table: see text]

1027 Background: Imlunestrant is a next-generation, oral SERD designed to deliver continuous ER-target inhibition. In the first-in-human Phase 1a/b EMBER study (NCT04188548), imlunestrant demonstrated favourable safety, PK, and clinical benefit when administered as monotherapy or with targeted therapy in ER+, HER2- aBC. Here we present clinical data of imlunestrant with HER2 targeted therapy, in patients (pts) with ER+, HER2+ aBC enrolled in EMBER. Methods: Pts were randomized to imlunestrant (400mg po daily) + trastuzumab (H), with or without (±) abemaciclib (Part C) or received maintenance treatment with imlunestrant + H + pertuzumab (P) (Part E), at standard doses in 21-day cycles. Key eligibility (Part C): ≥ 2 prior HER2 directed regimens, no prior CDK4/6i or fulvestrant; (Part E): received 1st line induction taxane chemotherapy (any duration) + H + P, without disease progression and ≤1 prior therapy for aBC. Key endpoints included safety, PK, ORR, CBR and PFS. Results: Overall, 45 pts with ER+/HER2+ aBC received the following combinations: imlunestrant + H (n=18), imlunestrant + H + abemaciclib (n=21; 1 pt received 800 mg imlunestrant), and imlunestrant + H + P (n=6). Baseline characteristics, safety, and preliminary efficacy are presented below (Table). Most TEAEs were grade 1-2. Common TEAEs with imlunestrant + H were fatigue (33%) and nausea (28%); with imlunestrant + H + abemaciclib were diarrhea (100%), neutropenia (57%), fatigue (52%) and nausea (48%); and with imlunestrant + H + P were diarrhea (50%) and arthralgia (50%). Imlunestrant PK was consistent with those previously reported with no drug-drug interactions observed with the combinations. From Part C, sequencing of baseline plasma ctDNA samples (n=37) identified prevalent mutations in TP53 (49%), PIK3CA (30%), ESR1 (24%), and GATA3 (14%). Clinical activity of imlunestrant in this ER+/HER2+ population, while based on small numbers, is promising. Conclusions: Imlunestrant in combination with trastuzumab ± abemaciclib or pertuzumab was well tolerated, showed no drug-drug interactions, and demonstrated preliminary antitumor activity in pts with ER+/HER2+ aBC. Clinical trial information: NCT04188548 . [Table: see text]

Abstract Background The current first-line (1L) standard of care (SOC) for human epidermal growth factor receptor 2-positive (HER2+) metastatic breast cancer (MBC) is trastuzumab (T) plus pertuzumab (P) and a taxane. Despite advances in 1L SOC, most patients progress during maintenance therapy with T+P. Tucatinib is a tyrosine kinase inhibitor (TKI) approved in combination with T and capecitabine for adults with HER2+ MBC, with and without brain metastases (BM). In HER2CLIMB, addition of tucatinib significantly prolonged progression-free survival (PFS) and overall survival (OS) in patients with HER2+ MBC and was well tolerated. Adding tucatinib also reduced the risk of disease progression or death in patients with untreated and/or active BM (Murthy et al. NEJM 2020, Curigliano et al. Ann Oncol 2022). HER2CLIMB-05 investigates whether adding tucatinib to 1L SOC as maintenance therapy will extend PFS while maintaining quality of life (QOL). Methods HER2CLIMB-05 (NCT05132582) is a phase 3, randomized, double-blind study evaluating tucatinib plus T+P as maintenance therapy for HER2+ MBC. Approximately 650 patients will be enrolled. Eligible patients will have advanced HER2+ disease, no progression on 4–8 cycles of prior 1L SOC, Eastern Cooperative Oncology Group Performance Status of 0 or 1, and no or asymptomatic BM. Exclusion criteria include prior treatment with anti-HER2 and/or anti-epidermal growth factor receptor TKI (prior SOC for early BC is permitted) or inability to undergo contrast magnetic resonance imaging of the brain. Patients will be randomized 1:1 to receive either tucatinib or placebo twice daily, with T+P once every 21 days. Patients with hormone receptor-positive disease may receive endocrine therapy. The primary endpoint is investigator-assessed PFS. Secondary endpoints include OS, time to deterioration of health-related QOL, central nervous system PFS, safety, and pharmacokinetic (PK) parameters. PFS and OS will be compared using a two-sided stratified log-rank test between treatment groups. Time-to-event endpoints will be summarized using the Kaplan–Meier method. PK and safety data will be summarized using descriptive statistics. Enrollment is ongoing in Austria, Chile, Greece, Italy, Japan, Poland, Portugal, Spain, the US, and several other European, APAC, and LATAM countries. This abstract was previously presented at ESMO-BC 2022, FPN (Final Publication Number): 415, by Veronique Dieras (reused with permission). Citation Format: Erika Hamilton, Junji Tsurutani, Giuseppe Curigliano, Miguel Martín, Ciara O'Sullivan, Joo Hyuk Sohn, Konstantinos Tryfonidis, Libero Santarpia, Shan Yang, Véronique Diéras. Phase 3 Study of Tucatinib or Placebo in Combination With Trastuzumab and Pertuzumab as Maintenance Therapy for HER2+ Metastatic Breast Cancer (HER2CLIMB-05, Trial in Progress) [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO1-19-11.

Abstract Background: Abemaciclib is approved both for high-risk early breast cancer as well as advanced breast cancer (ABC) in the first- and second-line setting. In MONARCH 2, the addition of abemaciclib to fulvestrant significantly improved both progression-free survival (PFS) and overall survival (OS) in patients with HR+, HER2- ABC with disease progression on prior endocrine therapy (ET). In MONARCH 3, the addition of abemaciclib to a nonsteroidal aromatase inhibitor (NSAI) significantly improved PFS (HR, 0.540; 95% CI, 0.418-0.698; p=0.000002) as initial therapy in HR+, HER2- ABC. At the last interim OS analysis (~252 events, at 5.8 years follow-up [FU]), a numerically favorable median OS difference (12.6 months) was observed (HR, 0.754; 95% CI, 0.584-0.974; p=0.0301, non-significant [NS]). Here, we present the final OS analysis of MONARCH 3 (NCT02246621). Methods: MONARCH 3 is a randomized, double-blind, Phase 3 study of abemaciclib + NSAI (anastrozole or letrozole) vs placebo + NSAI in postmenopausal women with HR+, HER2- ABC without prior systemic therapy in the advanced setting. OS was a gated secondary endpoint and chemotherapy-free survival (CFS) an exploratory endpoint. Final OS analysis was planned after approximately 315 OS events had occurred in the intent-to-treat (ITT) population with a split alpha between the ITT population and the subgroup with visceral disease (sVD) according to a prespecified graphical testing scheme. Kaplan-Meier method and stratified Cox proportional hazards models were used for time-to-event analyses. All reported p-values are two-sided. Results A total of 493 women were randomized 2:1 to receive abemaciclib + NSAI (n=328) or placebo + NSAI (n=165). After a median FU of 8.1 years, 7% of patients were still receiving treatment in the abemaciclib arm vs 3% in the placebo arm. In the ITT population, 314 OS events were observed (198 deaths among 328 patients [60%] in the abemaciclib arm and 116 among 165 [70%] in the placebo arm; HR, 0.804; 95% CI, 0.637-1.015; p=0.0664, NS). Median OS was 66.8 months in the abemaciclib arm and 53.7 months in the placebo arm, a numerical difference of 13.1 months in the ITT population. In the sVD, 178 events were observed (113 deaths among 173 patients [65%] in the abemaciclib arm and 65 among 90 [72%] in the placebo arm; HR, 0.758; 95% CI, 0.558-1.030; p=0.0757, NS). Median OS was 63.7 months in the abemaciclib arm and 48.8 months in the placebo arm, a numerical difference of 14.9 months in the sVD. Consistent OS differences were observed across prespecified subgroups. PFS benefit was sustained (median 29.0 vs 14.8 months; HR, 0.535; 95% CI, 0.429-0.668; nominal p&lt;0.0001) with substantial difference in 6-year PFS rates (23.3% vs 4.3% for abemaciclib vs placebo). CFS was also improved with abemaciclib vs placebo (median 46.7 vs 30.6 months; HR, 0.693; 95% CI, 0.557-0.863; nominal p=0.0010). No new safety signals were observed with longer term use. Conclusion In patients with HR+, HER2- ABC, abemaciclib in combination with a NSAI resulted in numerically longer OS compared to NSAI alone; however, statistical significance was not reached after a median FU of 8.1 years. The clinically meaningful improvement in median OS (&gt;13 months) combined with the sustained significant improvement in median PFS (&gt;14 months) and substantial extension in median CFS (&gt;16 months) continue to support the use of abemaciclib in combination with NSAI as first-line therapy in ABC. Citation Format: Matthew Goetz, Masakazu Toi, Jens Huober, Joo Hyuk Sohn, Olivier Trédan, Inhae Park, Mario Campone, Shin-Cheh Chen, Luis Manual Manso, Shani Paluch-Shimon, Orit C. Freedman, Valerie Andre, Abhijoy Saha, Gertjan van Hal, Ashwin Shahir, Hiroji Iwata, Stephen RD Johnston, Joyce O'Shaughnessy, Xavier Pivot, Sara Tolaney, Sara Hurvitz, Antonio Llombart. MONARCH 3: Final overall survival results of abemaciclib plus a nonsteroidal aromatase inhibitor as first-line therapy for HR+, HER2- advanced breast cancer [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr GS01-12.