Undisclosed CDK4/6 inhibitor

Adding the CDK4/6 inhibitor palbociclib enhanced the antitumor activity of EP0062 or fulvestrant in ESR1-mutant models but not in HER2-enriched or PTEN-mutant PDX models...EP0062 triggers an E2F1 downmodulation which mediates a potent antiproliferative activity. For EP0062-resistant tumors that remain ER-driven, the addition of palbociclib displays a potent antitumor effect.

FDA-approved sotorasib and adagrasib provide breakthrough therapies for cancer patients with KRASG12C mutation...Further enhanced anti-proliferation activity was observed when RGT-018 was combined with MEK, KRASG12C, EGFR or CDK4/6 inhibitors...Furthermore, RGT-018 overcame the resistance to the approved KRASG12C inhibitors caused by clinically acquired KRAS mutations either as a single agent or in combination. RGT-018 displayed promising pharmacological properties for combination with targeted agents to treat a broader KRAS-driven patient population.

However, studies have suggested that using aromatase inhibitors combined with CDK4/6-inhibitors might be an appropriate alternative in selected patients. Comprehensive molecular biology procedures, including sequential single-cell RNA-sequencing of tumor biopsies, are performed during 6 months of treatment with extensive biobanking of blood samples, tumor biopsies and gut microbiome specimens. Our findings will hopefully contribute to an improved selection of patients who may benefit from this drug combination and give new insights into the intra-tumoral changes during this treatment.Trial registration number: NCT05163106 (ClinicalTrials.gov).

Camizestrant also delivered strong antitumor activity in fulvestrant-resistant ESR1wt and ESR1m PDX models. Evaluation of camizestrant in combination with CDK4/6i (palbociclib or abemaciclib) in CDK4/6-naive and -resistant models, as well as in combination with PI3Kαi (alpelisib), mTORi (everolimus), or AKTi (capivasertib), indicated that camizestrant was active with CDK4/6i or PI3K/AKT/mTORi and that antitumor activity was further increased by the triple combination...The response was observed independently of PI3K pathway mutation status. Overall, camizestrant shows strong and broad anti-tumor activity in ER+ breast cancer as a monotherapy and when combined with CDK4/6i and PI3K/AKT/mTORi.

All had prior palbociclib + ET (2 pts had abemaciclib or ribociclib after palbociclib); a majority received fulvestrant (67%) and prior chemotherapy (50%). RGT-419B, with potent selective CDK4 activity, CDK2 activity and CDK6 selectivity, demonstrated a favorable safety and PK profile in an ongoing phase I study, with no grade 3 or higher TRAEs observed thus far. RGT-419B administered as once daily monotherapy also demonstrated preliminary evidence of efficacy as well. Dose expansions of RGT-419B as a single agent and in combination with ET in pts with HR+/HER2- ABC following prior CDK4/6i progression are planned.

DNADX was evaluated centrally in available baseline plasma ctDNA samples from PARSIFAL trial (NCT02491983) which randomized 486 patients (pts) with HR+/HER2- advanced breast cancer to receive (1:1 ratio) first line palbociclib with either fulvestrant or letrozole. Liquid biopsy-based DNADX subtypes predict outcomes in pts with HR+/HER2- advanced breast cancer on endocrine therapy and CDK4/6 inhibitors, potentially identifying the most optimal endocrine treatment for each pt.

Previous studies have suggested that narazaciclib (ON123300), a second-generation, orally bioavailable and clinical-stage CDK4/6 inhibitor (CDKi), may trigger cell cycle arrest and significant tumor growth inhibition (TGI) in BTKi-resistant MCL models...When combined with ibrutinib, but not with the second generation therapeutic acalabrutinib, narazaciclib achieved significant synergistic antitumor activity in both BTK-sensitive and BTK-resistant cells... Narazaciclib, due to its completely distinct MoA from BTKi involving the direct modulation of the cell cycle, can achieve significant synergistic activity with ibrutinib in vitro and in vivo, especially in BTKi-resistant models of MCL. Ongoing phospho-proteomics and genetic edition assays will help deciphering the molecular bases of this unique drug cooperation at the cell cycle level. Encore Abstract - previously submitted to AACR 2023

Selective CDK2 inhibitors have the potential to provide effective therapeutics for CDK2-dependent cancers and for combating drug resistance due to high cyclin E1 (CCNE1) expression intrinsically or CCNE1 amplification induced by treatment of CDK4/6 inhibitors...Here we report the discovery of a highly potent and selective macrocyclic CDK2 inhibitor QR-6401 (23) accelerated by the application of generative models and structure-based drug design (SBDD). QR-6401 (23) demonstrated robust antitumor efficacy in an OVCAR3 ovarian cancer xenograft model via oral administration.

To address this question, we have performed 0.5X shallow whole-genome sequencing in plasma from 459 patients with metastatic breast cancer, including 245 patients treated with endocrine therapy and a CDK4/6 inhibitor (ET + CDK4/6i) from 2 independent cohorts...More importantly, 4 DNA-based subtypes, and a ctDNA-based genomic signature tracking retinoblastoma loss-of-heterozygosity, are significantly associated with poor response and survival outcome following ET + CDK4/6i, independently of plasma tumor fraction. Our approach opens opportunities for the discovery of additional multi-feature genomic predictors coming from ctDNA in breast cancer and other cancer-types.

Here, we assessed the mechanisms of acquired resistance using T47D and MCF-7 tamoxifen- and palbociclib-resistant cell-line variants in culture and as xenografts, and patient-derived cells (PDCs) obtained from sensitive or resistant patient-derived xenografts (PDXs). In conclusion, we highlight the benefits of incorporating mTOR inhibitors into the current therapy in ER + breast cancer. This alternative therapeutic strategy not only enhances the antitumor response but may also delay the emergence of resistance and tumor recurrence.

Combination of the CDK4/6 inhibitor ribociclib with the PI3K inhibitor alpelisib showed antitumor activity in estrogen receptor-positive non-basal-like breast cancer patient-derived xenografts, independently of PIK3CA, ESR1 or RB1 mutation, also in drug de-escalation experiments or omitting endocrine therapy. Our results offer insights into predicting primary/acquired resistance to CDK4/6 inhibitors and post-progression therapeutic strategies.