Citations

Abstract Introduction: Epoxy fatty acid (EpFA) mechanisms of hormone therapy resistance (HTR) in ER+HER2- breast cancer (BC) are poorly understood. EETs are EpFAs that contribute to BC progression and HTR by promoting oxidative phosphorylation (OXPHOS). However, it remains unclear how EETs contribute to HTR. In this study, two fulvestrant resistant (FR) subclones of the letrozole resistant (LR) MCF-7AC1 line were isolated (termed LR/FR) and were incidentally resistant to the CDKi palbociclib (PR) (termed MCF-7AC1 LR/FR/PR or multiply resistant - MCF-7AC1 MR). These HTR cell lines exhibited CYP3A4 upregulation (2.3- to 4.3-fold) and increased cellular (±)14,15-EET levels, which were suppressed by biguanide treatment (P<0.05). Structure activity studies led to the design of hexyl cuban-1-yl biguanide (HCB) and fluorinated HCB derivatives C5F2-HCB and C6F3-HCB, which inhibited CYP3A4-mediated EET biosynthesis and growth of the HTR lines. HCB fluorination improved pharmacokinetics (PK) and toxicity. Methods: HCB and fluorinated HCBs were tested for impact on EET biosynthesis, OXPHOS, PK, and growth inhibition and reversal of hypoxia in the MCF-7AC1 MR tumor model. Results: Fulvestrant selection for MCF-7AC1 MR cell lines resulted in undetectable cyclin D1 and estrogen receptor (ERα) expression, while cyclin E1, CDK4, CDK6, CYP3A4, and c-MYC were upregulated (P<0.001). MCF-7 MR cells demonstrated 1.8, 1.4, and 1.2- fold higher levels of (±)8,9, (±)11,12, and (±)14,15-EET compared to parental MCF-7 cells (P<0.05). The most potent fluorinated HCB, C6F3-HCB, suppressed cellular levels of (±)8,9-EET, (±)11,12-EET, and (±)14,15-EET by 53-60% (P<0.029). The MCF-7AC1 MR cells were more potently inhibited by HCBs and fluorinated derivatives compared to the MCF-7 cell line. Comparing an MCF-7 MR line vs. MCF-7, HCB exhibited IC50 values of 4.1 vs. 7.0 uM, C5F2-HCB 10 vs. 25 uM, and C6F3-HCB 5.4 vs. 12 uM (P values all <0.05). C5F2-HCB exhibited the best PK and treatment of the MCF-7AC1 MR xenograft model showed reversal of hypoxia (P<0.05) and transient inhibition by C5F2-HCB (P=0.025 at 20 days). P/F also transiently inhibited this model (P=0.006 at 20 days). C5F2-HCB and P/F showed synergy in vitro (CI=0.46) leading to testing of C5F2-HCB/P/F in vivo enabled by acceptable toxicity of the triplet in mice. This combination showed synergy in vivo vs. standard of care palbociclib/fulvestrant by nonparametric statistical tests (Mann Whitney; P=0.0389; Kolmogorov-Smirnov; P=0.0473), providing a pathway for possible clinical development of the combination. Conclusions: MR BC cell lines exhibit upregulation of CYP3A4 and biosynthesis of EETs, indicating a role for EETs in HTR. The C5F2-HCB/P/F exhibits activity against the highly resistant MCF-7 MR xenograft with acceptable toxicity indicating an avenue for clinical development. Citation Format: Zhijun Guo, Jianxun Lei, Christian T. Wells, Allison M. Makovec, Andrew C. Yates, Swaathi Jayaraman, John R. Hawse, Joshua A. McCarra, Qing Cao, Michael J. Pryzbilla, Brenda L. Koniar, Beverly J. Norris, Craig M. Florey, Robert J. Schumacher, Michael A. Farrar, Kaylee L. Schwertfeger, Elizabeth A. Ambrose, Henry Wong, Gunda I. Georg, Antonino D'Assoro, Matthew P. Goetz, David A. Potter. Fluorinated cuban-1-yl biguanides overcome hormone therapy resistance to standard of care fulvestrant, and palbociclib [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(8_Suppl):Abstract nr LB196.

Abstract Background: Black men experience the highest burden of prostate cancer (CaP) incidence and mortality in the United States. The reasons documented for the significant burden of CaP in Black communities include health systems, care process, and individual/personal level factors, such as cultural factors, psychosocial factors, decision making/preferences, comprehension, past experience, and perceived behavioral control. The Community Living Lab (CoLLab) Learning Health System (LHS) was established within three American Legion Posts (ALP) in Northeast Florida to address these factors. Study Objective: This clinical trial study evaluated the impact of the CoLLab LHS on the knowledge, attitudes, beliefs, and cues to action of Black men who received Resources, Education, Amenities, and Community Health (REACH) services at the ALPs. Methods: The design was guided by the Intervention Mapping Framework and the Social Ecological Model. CoLLab REACH services were made available to participants through trusted community infrastructures. Services integrated include CaP resources and materials, social determinant of health navigation, healthy grocery distribution, cancer advocacy programs, and research participation. Participants were recruited at three ALPs and were asked to visit their respective CoLLab LHS site at least twice a month and up to 24 times over one year to use any of the services. The impact was measured using baseline and quarterly surveys assessing CaP awareness, knowledge, attitude, health beliefs, perceived control, intentions, and cues to action. Descriptive statistics were used to compare participants' information at baseline and at 3-month follow-up. Results: A total of 173 participants were included in this analysis; 57.9% were ≥ 60 years, and 92.2% were US-born Black men. Prostate cancer knowledge increased from baseline to 3-month follow-up. The median score rose from 4±1.29 at baseline, with the mean increasing to 4.24±1.10. Attitudes towards Cap screening declined marginally from 12.58±2.15 to 12.27±2.40. Health beliefs showed a clear upward shift, with the mean increasing from 22.86±3.0 at baseline to 23.20±2.82 after 3 months of intervention. Additionally, cues to action also improved, with the mean increasing from 2.78±1.67 to 3.25±1.45. Only the cues-to-action index showed a statistically significant difference (p = 0.018), with higher scores observed after 3 months of intervention. Conclusion: Across the four core constructs—prostate cancer knowledge, testing attitudes, health beliefs, and cues to action—outcomes at follow-up demonstrated modest but consistent improvements compared to those of baseline, alongside slightly reduced variability for most domains. Overall, the evaluation showed that CoLLab REACH services improved knowledge, enhanced stronger health beliefs, and significantly increased cues to action, while testing attitudes remained comparatively stable. Citation Format: Folakemi T. Odedina, Opeyemi Oreoluwa Bolajoko, Quincy A. Wimberly, Daniel W. Lee, Floyd B. Willis, Toshiko Moultrie, Wayne Ford, Derry Green, Arnold J. Merriweather, Michelle Fudge. The impact of the Community Living Lab learning health system on the prostate cancer knowledge, attitudes, beliefs, and cues to action of Black men [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(8_Suppl):Abstract nr LB324.

Abstract Background: Zedoresertib (zedo) and lunresertib (lunre) are oral, highly selective WEE1 and PKMYT1 inhibitors, respectively. Inhibition of these targets leads to premature mitotic entry, and in the presence of high replication stress causes mitotic catastrophe. In preclinical models, the combination of the zedo and lunre is synthetically lethal, supporting this first-in-class trial combination (NCT04855656). Methods: In this Phase 1 trial, patients (pts) with advanced solid tumors with CCNE1 amplification (amp), or FBXW7 or PPP2R1A deleterious mutations (mut) were treated with zedo (daily dosing) plus lunre (3 days on/4 days off), guided by preclinical modelling of the pharmacological contributions of WEE1 and PKMYT1 inhibition in achieving tumor regression. Objectives included safety, tolerability, recommended doses (RD), pharmacokinetics (PK), pharmacodynamics (PDy), antitumor activity and molecular response rate (MRR; ≥50% decline in circulating tumor DNA). Results: As of 18 Nov 2025, 54 pts (55.6% female ; prior lines of therapy 1 - 9, main cancer types: ovarian (OC) (35.2%), colorectal (31.5%), pancreatic (7.4%) and breast (5.6%)) were treated at 5 dose levels (DL) from 150 mg to 260 mg of zedo plus 60 mg or 80 mg of lunre. The most common ≥G3 treatment related adverse events (TRAEs) were anemia (9.3%), neutropenia (7.4%) and Palmar Plantar Erythrodysesthesia (PPE) (7.4%). There were no G5 TRAEs. 4 (9.3%) of 54 pts had a dose-limiting toxicity (G3 pain in extremity and G1 rash in same pt (zedo 150 mg / lunre 60 mg), G3 rash (200 mg / 80 mg), G3 PPE (260 mg / 60 mg), G3 vomiting (260 mg / 60 mg)). PK/PDy analyses showed dose-dependent exposures for both zedo and lunre and target engagement in most pts, with reductions in pCDK1 Thr14 and Tyr15 and yH2AX induction. 24 (55.5%) of 44 RECIST v1.1 evaluable pts showed tumor shrinkage (3 cCR, 5 uPR, 15 SD and 1 PD). Of 16 evaluable pts with advanced OC (12 platinum resistant , 2 unknown and 2 platinum sensitive) with CCNE1 amp (13 pts) or FBXW7 mut (3 pts), 13 (81.3%) showed tumor shrinkage (3 cCR, 3 uPR and 7 SD); clinical benefit rate (pts with CR, PR or SD) was 93.8%; 7 (43.8%) OC pts were on treatment for at least 16 weeks; 4 (25%) OC pts achieved GCIG CA-125 responses. Of 23 pts with a post baseline ctDNA analysis, a MRR of 39% was seen across all DLs. Conclusion: We report the first disclosure of clinical data of the first-in-field synthetic lethal combination of WEE1 and PKMYT1 inhibitors in a molecularly defined pt population. The safety profile of zedo and lunre was expected and manageable. Promising antitumor activity was observed in pts with CCNE1 amp or FBXW7 mut solid tumors, especially pts with OC. Further dose optimization of this combination is ongoing. Citation Format: Timothy A. Yap, Rahul Aggarwal, Elisa Fontana, Martin Hojgaard, Benedito A. Carneiro, Linda Duska, Patricia LoRusso, Siddhartha Yadav, Stephanie Lheureux, Cara Mathews, Ryan H. Moy, Nehal Lakhani, Mia Weiss, Joan Tymon-Rosario, Gerardo Colon-Otero, Ignacio Garrido-Laguna, Elisabeth K. Lee, Esteban Rodrigo Imedio, Jonathan Wessen, Luke Piggott, Vito Dozio, Noemie Luong, Christophe Mas, Alison M. Schram. First data disclosure of the Phase I trial of the first in class combination of WEE1 inhibitor zedoresertib with PKMYT1 inhibitor lunresertib in patients with advanced solid tumors harboring CCNE1, FBXW7, or PPP2R1A genomic alterations [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(8_Suppl):Abstract nr CT022.