AKT Inhibitor Capivasertib Research Articles

Proteomic profiling reveals CEACAM6 function in driving gallbladder cancer aggressiveness through integrin receptor, PRKCD and AKT/ERK signaling

Gallbladder cancer (GBC) presents as an aggressive malignancy with poor patient outcome. Like other epithelial cancers, the mechanisms of GBC cancer progression remain vague and efforts in finding targeted therapies fall below expectations. This study combined proteomic analysis of formalin-fixed paraffin-embedded (FFPE) GBC samples, functional and molecular characterization of potential oncogenes and identification of potential therapeutic strategies for GBC. We identified Carcinoembryonic Antigen-related Cell Adhesion Molecule 6 (CEACAM6) as one of the significantly most upregulated proteins in GBC. CEACAM6 overexpression has been observed in other cancer entities but the molecular function remains unclear. Our functional analyses in vitro and in vivo mouse models revealed that CEACAM6 supported the initial steps of cancer progression and metastasis by decreasing cell adhesion and promoting migration and invasion of GBC cells. Conversely, CEACAM6 knockdown abolished GBC aggressiveness by increasing cell adhesion while reducing cell migration, cell proliferation, and colony formation. BirA-BioID followed by mass-spectrometry revealed Integrin Beta-1 (ITGB1) and Protein Kinase C Delta (PRKCD) as direct molecular and functional partners of CEACAM6 supporting GBC cell migration. ERK and AKT signaling and their downstream target genes were regulated by CEACAM6 and thus the treatment with AKT inhibitor capivasertib or ERK inhibitor ulixertinib mitigated the CEACAM6-induced migration. These findings demonstrate that CEACAM6 is crucially involved in gallbladder cancer progression by promoting migration and inhibiting cell adhesion through ERK and AKT signaling providing specific options for treatment of CEACAM6-positive cancers.

Potent combination benefit of the AKT inhibitor capivasertib and the BCL-2 inhibitor venetoclax in diffuse large B cell lymphoma.

The therapeutic potential of targeting PI3K/AKT/PTEN signalling in B-cell malignancies remains attractive. Whilst PI3K-α/δ inhibitors demonstrate clinical benefit in certain B-cell lymphomas, PI3K signalling inhibitors have been inadequate in relapsed/refractory diffuse large B-cell lymphoma (DLBCL) in part, due to treatment related toxicities. Clinically, AKT inhibitors exhibit a differentiated tolerability profile offering an alternative approach for treating patients with B-cell malignancies. To explore how AKT inhibition complements other potential therapeutics in the treatment of DLBCL patients, an in vitro combination screen was conducted across a panel of DLCBL cell lines. The AKT inhibitor, capivasertib, in combination with the BCL-2 inhibitor, venetoclax, produced notable therapeutic benefit in preclinical models of DLBCL. Capivasertib and venetoclax rapidly induced caspase and PARP cleavage in GCB-DLBCL PTEN wildtype cell lines and those harbouring PTEN mutations or reduced PTEN protein, driving prolonged tumour growth inhibition in DLBCL cell line and patient derived xenograft lymphoma models. The addition of the rituximab further deepened the durability of capivasertib and venetoclax responses in a RCHOP refractory DLBCL in vivo models. These findings provide preclinical evidence for the rational treatment combination of AKT and BCL-2 inhibitors using capivasertib and venetoclax respectively alongside anti-CD20 antibody supplementation for treatment of patients with DLBCL.

Overcoming Osimertinib Resistance with AKT Inhibition in EGFRm-Driven Non-Small Cell Lung Cancer with PIK3CA/PTEN Alterations.

Osimertinib is an EGFR tyrosine kinase inhibitor indicated for the treatment of EGFR-mutated (EGFRm)-driven lung adenocarcinomas. Osimertinib significantly improves progression-free survival in first-line-treated patients with EGFRm advanced non-small cell lung cancer (NSCLC). Despite the durable disease control, the majority of patients receiving osimertinib eventually develop disease progression. ctDNA profiling analysis of on-progression plasma samples from patients treated with osimertinib in both first- (phase III, FLAURA trial) and second-line trials (phase III, AURA3 trial) revealed a high prevalence of PIK3CA/AKT/PTEN alterations. In vitro and in vivo evidence using CRISPR-engineered NSCLC cell lines and patient-derived xenograft (PDX) models supports a functional role for PIK3CA and PTEN mutations in the development of osimertinib resistance. These alterations are functionally relevant as EGFRm NSCLC cells with engineered PIK3CA/AKT/PTEN alterations develop resistance to osimertinib and can be resensitized by treatment with the combination of osimertinib and the AKT inhibitor capivasertib. Moreover, xenograft and PDX in vivo models with PIK3CA/AKT/PTEN alterations display limited sensitivity to osimertinib relative to models without alterations, and in these double-mutant models, capivasertib and osimertinib combination elicits an improved antitumor effect versus osimertinib alone. Together, this approach offers a potential treatment strategy for patients with EGFRm-driven NSCLC who have a suboptimal response or develop resistance to osimertinib through PIK3CA/AKT/PTEN alterations. See related commentary by Vokes et al., p. 3968.

The efficacy and safety of PI3K and AKT inhibitors for patients with cancer: A systematic review and network meta-analysis

BackgroundInhibiting PI3K/AKT pathway activation may hinder the occurrence and progression of cancer. The aim of this study was to evaluate the efficacy and safety of the PI3K/AKT inhibitors and determine the most appropriate inhibitor for different cancer types. MethodsElectronic databases up to June 2024 were used to examine the efficacy and safety of PI3K inhibitors (alpelisib, copanlisib, duvelisib, and idelalisib) and AKT inhibitors (capivasertib, ipatasertib and MK-2206) for the treatment of cancer. Data was assessed with a random-effect pairwise and network meta-analysis. Randomized controlled trials and retrospective studies were eligible if they compared PI3K or AKT inhibitors with non-PI3K/AKT controls with no restriction. ResultsThe results were based on 34 studies from 34 published articles and 6 online registration trials (6710 patients). According to pairwise meta-analysis, PI3K/AKT inhibitors showed to be highly effective, especially for treating mutant cancers, but had poor safety profiles. According to our network meta-analysis, PI3K/AKT inhibitors, especially the AKT inhibitor capivasertib, are effective for treating solid cancers such as breast cancer (BC). Moreover, PI3K inhibitors, especially idelalisib, were effective for treating hematologic cancers such as chronic lymphocytic leukemia (CLL). ConclusionsThe PI3K/AKT inhibitors are effective in patients with genetic mutations. For solid cancers such as BC, capivasertib was efficacy and safety. For hematological cancers represented by CLL, idelalisib was efficacy and safety. The above studies can be used when recommending appropriate targeted therapies for patients with different cancer types.

PIKing up and AKTing on Resistance Mutations in Osimertinib-Treated EGFR-Mutated NSCLC.

A recent study identified high rates of PI3K-AKT pathway mutations from the FLAURA and AURA3 osimertinib trials and pre-clinically validated that these mutations decreased osimertinib sensitivity in EGFR-mutated non-small cell lung cancer. The AKT inhibitor capivasertib was found to overcome this resistance, providing an important rationale for the development of AKT inhibitors in non-small cell lung cancer. See related article by Grazini et al., p. 4143.

Emerging drugs in breast cancer: a focus on antibody–drug conjugates and novel treatment options in luminal disease

SummaryRecent years have seen the introduction of several new drugs and novel treatment approaches in early and advanced-stage breast cancer, leading to relevant improvements in outcome. Still, further reduction of recurrence risk in high-risk early breast cancer is required as is further improvement of disease control in metastatic disease, preferentially with parallel improvement of tolerability. Several antibody–drug conjugates are currently under clinical development, among them drugs targeting HER2, HER3 and TROP2; in addition, bispecific HER2-directed antibodies are a promising class of drugs. In hormone receptor-positive disease, optimizing treatment options in patients progressing on prior CDK4/6-inhibitor-based therapies is a focus of clinical research and recent developments encompass small molecule growth-factor pathway inhibitors such as the AKT inhibitor capivasertib, novel PIK3Ca inhibitors such as inavolisib as well as selective oestrogen receptor degraders and modulators. This article is intended as a short review of promising novel drugs in later clinical development in the field of breast cancer.

Interruption of KLF5 acetylation promotes PTEN-deficient prostate cancer progression by reprogramming cancer-associated fibroblasts.

Inactivation of phosphatase and tensin homolog (PTEN) is prevalent in human prostate cancer and causes high-grade adenocarcinoma with a long latency. Cancer-associated fibroblasts (CAFs) play a pivotal role in tumor progression, but it remains elusive whether and how PTEN-deficient prostate cancers reprogram CAFs to overcome the barriers for tumor progression. Here, we report that PTEN deficiency induced Krüppel-like factor 5 (KLF5) acetylation and that interruption of KLF5 acetylation orchestrated intricate interactions between cancer cells and CAFs that enhance FGF receptor 1 (FGFR1) signaling and promote tumor growth. Deacetylated KLF5 promoted tumor cells to secrete TNF-α, which stimulated inflammatory CAFs to release FGF9. CX3CR1 inhibition blocked FGFR1 activation triggered by FGF9 and sensitized PTEN-deficient prostate cancer to the AKT inhibitor capivasertib. This study reveals the role of KLF5 acetylation in reprogramming CAFs and provides a rationale for combined therapies using inhibitors of AKT and CX3CR1.

Capivasertib in combination with enzalutamide for metastatic castration resistant prostate cancer after docetaxel and abiraterone: Results from the randomized phase II RE-AKT trial

BackgroundPTEN loss and aberrations in PI3K/AKT signaling kinases associate with poorer response to abiraterone acetate (AA) in metastatic castration-resistant prostate cancer (mCRPC). In this study, we assessed antitumor activity of the AKT inhibitor capivasertib combined with enzalutamide in mCRPC with prior progression on AA and docetaxel. MethodsThis double-blind, placebo-controlled, randomized phase 2 trial, recruited men ≥ 18 years with progressing mCRPC and performance status 0–2 from 15 UK centers. Randomized participants (1:1) received enzalutamide (160 mg orally, once daily) with capivasertib (400 mg)/ placebo orally, twice daily on an intermittent (4 days on, 3 days off) schedule. Primary endpoint was composite response rate (RR): RECIST 1.1 objective response, ≥ 50 % PSA decrease from baseline, or circulating tumor cell count conversion (from ≥ 5 at baseline to < 5 cells/7.5 mL). Subgroup analyses by PTENIHC status were pre-planned. ResultsOverall, 100 participants were randomized (50:50); 95 were evaluable for primary endpoint (47:48); median follow-up was 43 months. RR were 9/47 (19.1 %) enzalutamide/capivasertib and 9/48 (18.8 %) enzalutamide/placebo (absolute difference 0.4 % 90 %CI −12.8 to 13.6, p = 0.58), with similar results in the PTENIHC loss subgroup. Irrespective of treatment, OS was significantly worse for PTENIHC loss (10.1 months [95 %CI: 4.6–13.9] vs 14.8 months [95 %CI: 10.8–18]; p = 0.02). Most common treatment-emergent grade ≥ 3 adverse events for the combination were diarrhea (13 % vs 2 %) and fatigue (10 % vs 6 %). ConclusionsCombined capivasertib/enzalutamide was well tolerated but didn’t significantly improve outcomes from abiraterone pre-treated mCRPC.

Abstract LB450: Mechanisms of acquired resistance to AKT inhibitor capivasertib in AKT1 mutant patient derived breast cancer models

Abstract Capivasertib, a pan-AKT inhibitor, has recently been approved in combination with fulvestrant to treat ER+ HER2- breast cancer patients with one or more of PI3KCA/AKT1/PTEN alterations. However, as with many targeted therapies acquired drug resistance remains a challenge. In this study, we investigated the mechanisms of acquired capivasertib resistance in AKT1 mutant breast cancer models. We established two estrogen receptor positive (ER+) AKT1 E17K mutant breast cancer patient derived organoids (PDOs), that were sensitive to capivasertib in vitro. PDOs were chronically exposed to 1µM capivasertib. PDOs were sequenced (DNA &amp; RNA) at multiple timepoints of treatment (3 days, 4 and 9 weeks after development of resistance). Using CRISPR-Cas9 editing we also engineered CAMA1 (ER+) cells to express AKT1 E17K, and generated derived resistant AKT1 mutant and parental models in response to continuous capivasertib exposure. CAMA1 AKT1 mutant and parental resistant were screened with an siRNA Kinome library supplemented with genes from the PDO RNA-sequencing. Phosphoproteomics was performed on capivasertib resistant E17K models in the presence and absence of capivasertib. PDO models persisting after either 4 or 9 weeks of capivasertib treatment showed no acquisition of genetic driver events, or changes in AKT copy number. Resistant organoids at 9 weeks treatment showed increased expression of ERBB3 (HER3), EGFR3 and LPAR5 as well as increased expression of MAPK signalling components. In siRNA screens on CAMA1 derived resistant models, siRNA targeting ERBB2, CDK4, PLK4 and CHEK1, ESR1 and LPAR5 modulated sensitivity to capivasertib. Analysis of phosphoproteins in capivasertib resistant models revealed reactivation of mTORC1 signalling despite sustained AKT inhibition, with dramatic upregulation of PDK1 and mTORC2. Consistent with the siRNA screens, drug combinations identified fulvestrant as a synergistic agent with capivasertib in the resistant E17K models. Sensitivity to mTOR inhibition was maintained in capivasertib resistant models, with mTOR inhibition re-sensitizing cells to capivasertib. In these models, acquired resistance to capivasertib occurs through upregulation of ER signalling and rewiring of pathway signalling to bypass AKT inhibition and reactivate mTORC1. Targeting these mechanisms could prolong the use of capivasertib, with future work focusing on validating these mechanisms and re-sensitizing drug combinations in other AKT1 mutant models &amp; PDOs. Citation Format: Sarah Mearns, Alex Pearson, Li-Xuan Sim, Rosalind Cutts, Prithika Sritharan, Heena Shah, Aditi Gulati, Stuart Williamson, Simon Barry, Elza De-Bruin, Nicholas C. Turner. Mechanisms of acquired resistance to AKT inhibitor capivasertib in AKT1 mutant patient derived breast cancer models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(7_Suppl):Abstract nr LB450.

MiR-4649-5p acts as a tumor-suppressive microRNA in triple negative breast cancer by direct interaction with PIP5K1C, thereby potentiating growth-inhibitory effects of the AKT inhibitor capivasertib

BackgroundTriple negative breast cancer (TNBC) is a particularly aggressive and difficult-to-treat subtype of breast cancer that requires the development of novel therapeutic strategies. To pave the way for such developments it is essential to characterize new molecular players in TNBC. MicroRNAs (miRNAs) constitute interesting candidates in this regard as they are frequently deregulated in cancer and contribute to numerous aspects of carcinogenesis.Methods and resultsHere, we discovered that miR-4649-5p, a miRNA yet uncharacterized in breast cancer, is associated with better overall survival of TNBC patients. Ectopic upregulation of the otherwise very low endogenous expression levels of miR-4646-5p significantly decreased the growth, proliferation, and migration of TNBC cells. By performing whole transcriptome analysis and physical interaction assays, we were able to identify the phosphatidylinositol phosphate kinase PIP5K1C as a direct target of miR-4649-5p. Downregulation or pharmacologic inhibition of PIP5K1C phenocopied the growth-reducing effects of miR-4649-5p. PIP5K1C is known to play an important role in migration and cell adhesion, and we could furthermore confirm its impact on downstream PI3K/AKT signaling. Combinations of miR-4649-5p upregulation and PIP5K1C or AKT inhibition, using the pharmacologic inhibitors UNC3230 and capivasertib, respectively, showed additive growth-reducing effects in TNBC cells.ConclusionIn summary, miR-4649-5p exerts broad tumor-suppressive effects in TNBC and shows potential for combined therapeutic approaches targeting the PIP5K1C/PI3K/AKT signaling axis.

Combining the AKT inhibitor capivasertib and SERD fulvestrant is effective in palbociclib-resistant ER+ breast cancer preclinical models

Combining the selective AKT inhibitor, capivasertib, and SERD, fulvestrant improved PFS in a Phase III clinical trial (CAPItello-291), treating HR+ breast cancer patients following aromatase inhibitors, with or without CDK4/6 inhibitors. However, clinical data suggests CDK4/6 treatment may reduce response to subsequent monotherapy endocrine treatment. To support understanding of trials such as CAPItello-291 and gain insight into this emerging population of patients, we explored how CDK4/6 inhibitor treatment influences ER+ breast tumour cell function and response to fulvestrant and capivasertib after CDK4/6 inhibitor treatment. In RB+, RB− T47D and MCF7 palbociclib-resistant cells ER pathway ER and Greb-1 expression were reduced versus naïve cells. PI3K-AKT pathway activation was also modified in RB+ cells, with capivasertib less effective at reducing pS6 in RB+ cells compared to parental cells. Expression profiling of parental versus palbociclib-resistant cells confirmed capivasertib, fulvestrant and the combination differentially impacted gene expression modulation in resistant cells, with different responses seen in T47D and MCF7 cells. Fulvestrant inhibition of ER-dependent genes was reduced. In resistant cells, the combination was less effective at reducing cell cycle genes, but a consistent reduction in cell fraction in S-phase was observed in naïve and resistant cells. Despite modified signalling responses, both RB+ and RB− resistant cells responded to combination treatment despite some reduction in relative efficacy and was effective in vivo in palbociclib-resistant PDX models. Collectively these findings demonstrate that simultaneous inhibition of AKT and ER signalling can be effective in models representing palbociclib resistance despite changes in pathway dependency.

Capivasertib in Hormone Receptor–Positive Advanced Breast Cancer

BackgroundAKT pathway activation is implicated in endocrine-therapy resistance. Data on the efficacy and safety of the AKT inhibitor capivasertib, as an addition to fulvestrant therapy, in patients with hormone receptor–positive advanced breast cancer are limited.MethodsIn a phase 3, randomized, double-blind trial, we enrolled eligible pre-, peri-, and postmenopausal women and men with hormone receptor–positive, human epidermal growth factor receptor 2–negative advanced breast cancer who had had a relapse or disease progression during or after treatment with an aromatase inhibitor, with or without previous cyclin-dependent kinase 4 and 6 (CDK4/6) inhibitor therapy. Patients were randomly assigned in a 1:1 ratio to receive capivasertib plus fulvestrant or placebo plus fulvestrant. The dual primary end point was investigator-assessed progression-free survival assessed both in the overall population and among patients with AKT pathway–altered (PIK3CA, AKT1, or PTEN) tumors. Safety was assessed.ResultsOverall, 708 patients underwent randomization; 289 patients (40.8%) had AKT pathway alterations, and 489 (69.1%) had received a CDK4/6 inhibitor previously for advanced breast cancer. In the overall population, the median progression-free survival was 7.2 months in the capivasertib–fulvestrant group, as compared with 3.6 months in the placebo–fulvestrant group (hazard ratio for progression or death, 0.60; 95% confidence interval [CI], 0.51 to 0.71; P<0.001). In the AKT pathway–altered population, the median progression-free survival was 7.3 months in the capivasertib–fulvestrant group, as compared with 3.1 months in the placebo–fulvestrant group (hazard ratio, 0.50; 95% CI, 0.38 to 0.65; P<0.001). The most frequent adverse events of grade 3 or higher in patients receiving capivasertib–fulvestrant were rash (in 12.1% of patients, vs. in 0.3% of those receiving placebo–fulvestrant) and diarrhea (in 9.3% vs. 0.3%). Adverse events leading to discontinuation were reported in 13.0% of the patients receiving capivasertib and in 2.3% of those receiving placebo.ConclusionsCapivasertib–fulvestrant therapy resulted in significantly longer progression-free survival than treatment with fulvestrant alone among patients with hormone receptor–positive advanced breast cancer whose disease had progressed during or after previous aromatase inhibitor therapy with or without a CDK4/6 inhibitor. (Funded by AstraZeneca and the National Cancer Institute; CAPItello-291 ClinicalTrials.gov number, NCT04305496.)

Abstract 5321: Large scale pan cancer drug combination screening to identify effective and actionable combinations and biomarker hypothesis

Abstract Drug combinations are highly desirable in oncology as they can improve therapeutic response and overcome drug resistance. However, responses can be context-specific, meaning there is a real need for large-scale studies to fully explore the drug combination response landscape. We present a screen of 109 drug combinations in over 750 diverse cell lines covering 41 hematological and solid tumor types. Each combination was screened in a full 7 × 7 matrix format, representing over 2.3 million individual data points, the largest such study to date. We took a novel approach to assess combination benefit. Growth inhibition and highest single agent (HSA) and Bliss excess combination heatmaps were generated for all &amp;gt;68,000 combination-cell line pairs, and each was scored for high activity (combination Emax&amp;gt;0.5) and combination benefit/synergy (HSA&amp;gt;0.1). Out of 4578 combination-cancer type pairs 489 met the filtering criteria. We prioritized combinations based on their efficacy and cancer type selectivity to minimize risk of potential tissue toxicity. We identified several known combination-cancer type pairs (e.g. MCL1 inhibitor AZD5991 plus BCL2 inhibitor venetoclax in AML) as well as novel indications for combinations already known to be active in a different cancer type (e.g. AZD5991 plus AKT inhibitor capivasertib in endometrial cancer or AURKB inhibitor AZD2811 plus venetoclax in DLBCL). We selected 4 combinations based on clinical need and validated them further in vitro and in vivo (selumetinib plus venetoclax or AZD5991, AZD2811 plus venetoclax, and capivasertib plus AZD5991). To understand how molecular context affects drug response, we also used GDSC tools ANOVA to perform over 5.4 million statistical tests to identify statistically significant associations between drug response metrics and multi-omics features including mutations, CNAs, gene expression and methylation. Associations were identified with five response metrics, covering both single agent and combination responses. We looked for significant associations across 21 different subgroups of cell lines and 6 molecular ‘baskets’ (TP53, KRAS, MLL2/KMT2D, PTEN, PIK3CA, and BRAF). We identified 11,611 biomarkers which met the significance criteria (p⇐0.001, FDR⇐10%, and both positive and negative Glass deltas &amp;gt;=1). Moreover, we used biomarkers of single-agent response to identify any combination Emax or Bliss associated biomarkers that could not be explained by the action of either drug. This resulted in identification of 1,631 ‘emergent’ biomarkers. In summary, our screen and pipeline have been designed to optimize preclinical interpretation with a focus on actionability, particularly by our unique approach, and to provide a valuable resource for exploration by the wider research community. As a result of this screen, we identified and validated novel combination-tumor types in multiple cancer types. Citation Format: Azadeh Bashi, Elizabeth A. Coker, Krishna Bulusu, Marta Milo, Claire Crafter, James Lynch, David Jenkins, Howard Lightfoot, Brandon Willis, Courtney Andersen, Omid Tavana, Kevin Mongeon, Jacob Gordon, Paul Smith, Simon Barry, Ultan McDermott, Lisa Drew, Susan Critchlow, Mathew J. Garnett, Jerome Mettetal. Large scale pan cancer drug combination screening to identify effective and actionable combinations and biomarker hypothesis. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 5321.

Filling the Gap after CDK4/6 Inhibitors: Novel Endocrine and Biologic Treatment Options for Metastatic Hormone Receptor Positive Breast Cancer.

The rise of cyclin-dependent kinase (CDK)4/6 inhibitors has rapidly reshaped treatment algorithms for hormone receptor (HR)-positive metastatic breast cancer, with endocrine treatment (ET) plus a CDK4/6-inhibitor currently representing the standard of care in the first line setting. However, treatment selection for those patients experiencing progression while on ET + CDK4/6-inhibitors remains challenging due to the suboptimal activity or significant toxicities of the currently available options. There is also a paucity of data regarding the efficacy of older regimens, such as everolimus + exemestane, post-CDK4/6 inhibition. In this setting of high unmet need, several clinical trials of novel drugs have recently reported encouraging results: the addition of the AKT-inhibitor capivasertib to fulvestrant demonstrated a significant improvement in progression-free survival (PFS); the oral selective estrogen receptor degrader (SERD) elacestrant prolonged PFS compared to traditional ET in a phase 3 trial, particularly among patients with detectable ESR1 mutations; finally, PARP inhibitors are available treatment options for patients with pathogenic BRCA1/2 germline mutations. Overall, a plethora of novel endocrine and biologic treatment options are finally filling the gap between first-line ET and later line chemotherapy. In this review article, we recapitulate the activity of these novel treatment options and their potential role in future treatment algorithms.

Abstract PD10-04: PD10-04 Combination of the next generation oral SERD camizestrant (AZD9833) with CDK4/6 and mTOR/AKT inhibitors delivers robust efficacy in a broad range of ER+ breast tumors

Abstract Next-generation oral selective estrogen receptor degraders (ngSERDs) are aiming to become the backbone endocrine therapy (ET) for patients with estrogen receptor positive (ER+) breast cancer (BC) by achieving greater ER signaling blockade than current therapies and tackling key mechanisms of resistance. Camizestrant (AZD9833) is an ngSERD for the treatment of ER+ BC which has demonstrated selective ERα degradation, pure ER antagonism and significant anti-tumor activity in ESR1 wild-type (ESR1wt) and mutant (ESR1m) tumors, as well as encouraging clinical activity in early phase trials. ER+ BC is responsive to therapies targeting ER and CDK4/6 signaling in the adjuvant and metastatic settings. To explore camizestrant combination potential as a backbone ET, camizestrant was partnered with either palbociclib or abemaciclib in CDK4/6 inhibitor (CDK4/6i) naïve and resistant in vitro and in vivo models. Combination benefit was observed in vitro in 3 parental ER+ BC cell lines, moreover camizestrant plus abemaciclib showed activity in palbociclib-resistant cell lines including lines harboring CCNE1amp and RB1 loss. In vivo, combination of camizestrant and either CDK4/6i was well tolerated with the combinations promoting improved efficacy in ESR1wt and ESR1m PDX tumor models compared to monotherapy arms. ER+ BC has a high prevalence of alterations in the PI3K/AKT/PTEN pathway which provides opportunities for treatment with PI3K/AKT pathway inhibitors. Camizestrant delivered enhanced efficacy when combined with mTORC1 inhibitor everolimus and AKT inhibitor capivasertib in CTC-174, an ESR1m and PI3KCAm tumor model. Additionally, combination with capivasertib was more efficacious than single treatments, at clinically relevant dose and schedules, in both PI3Kwt and mutated pathway in PDX models. These data demonstrate the interplay between PI3K/AKT/PTEN pathway inhibition and camizestrant mechanism of action. Finally, we explored a potential triple combination of camizestrant, capivasertib and palbociclib in Palbociclib-resistant models representative of PI3KCA/AKT/PTEN wt and altered tumors. This strategy delivered robust efficacy across these models comparing to single treatments and double combinations. The triplet led to durable regressions at clinically achievable doses of all compounds, irrespective of genetic background and aligned to biomarker modulation of the three signaling axis. These preclinical data demonstrate the potential of camizestrant to become the backbone ET, with high combinability in vivo with inhibitors of CDK4/6, mTOR and AKT. These combinations demonstrate the opportunity to impact care of patients with early and metastatic ER+BC, delivering benefit to broad patient populations including those with ESR1wt or ESR1m tumors, independent of PI3K/AKT/PTEN pathway mutation status, and in patients with both CDK4/6i sensitive and resistant tumors. Citation Format: Larissa Carnevalli, Susana Ros, Jelena Urosevic, Natalie Cureton, Sophie Darcy, Mandy Lawson, Stuart Williamson, Pablo Morentin Gutierrez, Azadeh Bashi, Jennifer Moss, Christopher Morrow, Barry Simon, Teresa Klinowska. PD10-04 Combination of the next generation oral SERD camizestrant (AZD9833) with CDK4/6 and mTOR/AKT inhibitors delivers robust efficacy in a broad range of ER+ breast tumors. [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr PD10-04.

ASCO 2022 Breast Cancer Updates

"Data presented at ASCO 2022 provide new perspectives of therapy for patients with breast cancer. Starting with the plenary session with DESTINY-Breast04 we are turning a new page in the treatment of metastatic human epidermal growth factor receptor 2 (HER2)-low breast cancer patients. The results of the DESTINY-Breast04 trial open a new therapeutic option for half of the patients with metastatic breast cancer, establishing HER2-low metastatic breast cancer as a targetable population with trastuzumab deruxtecan. The indications for antibody drug conjugates are expanding to patients with metastatic hormone receptor positive endocrine resistant disease based on TROPICS-02. From the multitude of clinical trials with antibody drug conjugates, we can envision that this will be likely the new way to deliver chemotherapy in the future. Differences in survival within the three cyclin-dependent kinase 4/6 (CDK4/6) inhibitors in upfront metastatic hormone positive breast cancer are emerging. We have data on continuation of ribociclib beyond disease progression on CDK4/6 in the MAINTAIN trial. The FAKTION trial does prove the benefit of the AKT inhibitor capivasertib and does highlight the importance of an extended molecular panel of the phosphatidylinositol3-kinase PI3K pathway. Furthermore, the exploratory analysis of KEYNOTE- 522, examining the correlation of event free survival and residual cancer burden after neoadjuvant treatment in patients with triple negative breast cancer does demonstrate a benefit of pembrolizumab extending to patient which did not achieve pathologic complete response, mainly by a decrease in residual cancer burden. Advances in biomarkers of response to immunotherapy are needed. For early stage breast cancer studies are in support of de-escalation of radiotherapy for low risk breast cancer patients and confirming the lack of benefit of adjuvant chemotherapy for elderly patients, even with high genomic grade index."

WIN Symposium 2022 - Abstract Poster Presentations.

WIN Symposium 2022 - Abstract Poster Presentations.

AKT mutant allele-specific activation dictates pharmacologic sensitivities

AKT- a key molecular regulator of PI-3K signaling pathway, is somatically mutated in diverse solid cancer types, and aberrant AKT activation promotes altered cancer cell growth, survival, and metabolism1–8. The most common of AKT mutations (AKT1 E17K) sensitizes affected solid tumors to AKT inhibitor therapy7,8. However, the pathway dependence and inhibitor sensitivity of the long tail of potentially activating mutations in AKT is poorly understood, limiting our ability to act clinically in prospectively characterized cancer patients. Here we show, through population-scale driver mutation discovery combined with functional, biological, and therapeutic studies that some but not all missense mutations activate downstream AKT effector pathways in a growth factor-independent manner and sensitize tumor cells to diverse AKT inhibitors. A distinct class of small in-frame duplications paralogous across AKT isoforms induce structural changes different than those of activating missense mutations, leading to a greater degree of membrane affinity, AKT activation, and cell proliferation as well as pathway dependence and hyper-sensitivity to ATP-competitive, but not allosteric AKT inhibitors. Assessing these mutations clinically, we conducted a phase II clinical trial testing the AKT inhibitor capivasertib (AZD5363) in patients with solid tumors harboring AKT alterations (NCT03310541). Twelve patients were enrolled, out of which six harbored AKT1-3 non-E17K mutations. The median progression free survival (PFS) of capivasertib therapy was 84 days (95% CI 50-not reached) with an objective response rate of 25% (n = 3 of 12) and clinical benefit rate of 42% (n = 5 of 12). Collectively, our data indicate that the degree and mechanism of activation of oncogenic AKT mutants vary, thereby dictating allele-specific pharmacological sensitivities to AKT inhibition.

Galvanotactic Migration of Glioblastoma and Brain Metastases Cells.

Galvanotaxis, the migration along direct current electrical fields, may contribute to the invasion of brain cancer cells in the tumor-surrounding tissue. We hypothesized that pharmacological perturbation of the epidermal growth factor (EGF) receptor and downstream phosphatidylinositol 3-kinase (PI3K)/AKT pathway prevent galvanotactic migration. In our study, patient-derived glioblastoma and brain metastases cells were exposed to direct current electrical field conditions. Velocity and direction of migration were estimated. To determine the effects of EGF receptor antagonist afatinib and AKT inhibitor capivasertib, assays of cell proliferation, apoptosis and immunoblot analyses were performed. Both inhibitors attenuated cell proliferation in a dose-dependent manner and induced apoptosis. We found that most of the glioblastoma cells migrated preferentially in an anodal direction, while brain metastases cells were unaffected by direct current stimulations. Afatinib presented only a mild attenuation of galvanotaxis. In contrast, capivasertib abolished the migration of glioblastoma cells without genetic alterations in the PI3K/AKT pathway, but not in cells harboring PTEN mutation. In these cells, an increase in the activation of ERK1/2 may in part substitute the inhibition of the AKT pathway. Overall, our data demonstrate that glioblastoma cells migrate in the electrical field and the PI3K/AKT pathway was found to be highly involved in galvanotaxis.

Abstract PD3-07: Combined inhibition of CDK4/6 and AKT is effective in Rb-intact triple-negative breast cancer of the luminal androgen receptor (LAR) subtype

Abstract Background: Triple-negative breast cancer (TNBC) is a heterogeneous disease group with variable clinico-pathologic features. Based on gene expression profiles, TNBCs are grouped into 6 major subtypes. The Luminal androgen receptor (LAR) subtype is enriched for potentially targetable biomarkers, including high androgen receptor (AR) expression, high rates of PIK3CA mutations, and intact Rb. The purpose of this study was to investigate the most effective combinations of CDK4/6, AR, and PI3K-AKT inhibitors in pre-clinical models of LAR TNBC for future clinical trial design. Methods: MDA-MB-453 and MFM-223 (both Rb-intact/PTEN-intact/PIK3CA-mutant) and CAL-148 (Rb-null/PTEN-null/PIK3CA-mutant) LAR TNBC cell lines were treated with the CDK4/6 inhibitor palbociclib, the PI3Kα inhibitor alpelisib, the AKT inhibitor capivasertib, and the AR antagonist enzalutamide, each alone or in different combinations. Drug sensitivity was determined by coulter counter cell counts in 2D, colony formation, and the CellTiterGlo cell viability assay. The combination index (CI) which defines synergism (CI &amp;lt; 1), additive effect (CI = 1) and antagonism (CI &amp;gt; 1), calculated by the CompuSyn method, was used to evaluate the synergistic effects of drug combinations. Expression of cell cycle and PI3K-AKT downstream signaling molecules was measured by western blot analysis. An androgen response element (ARE) luciferase-based reporter assay was used to evaluate AR transcriptional activity. Results: Rb-intact LAR TNBC cell lines were sensitive to single-agent palbociclib, alpelisib or capivasertib (IC50, ~500 nM). Enzalutamide had minimal growth inhibitory activity (IC50, 15-25 μM). Palbociclib combined with either alpelisib or capivasertib synergistically inhibited proliferation of LAR TNBC cells (CI values, 0.07-0.86). Treatment of Rb-intact LAR TNBC cells with palbociclib monotherapy suppressed Rb phosphorylation and resulted in adaptive phosphorylation/activation of S473 AKT and AKT substrates GSKβ and PRAS40 at 24h. These responses were not observed in Rb-null CAL-148 cells. Palbociclib-induced phosphorylation of AKT substrates as well as induction P-S6 and P-4EBP1 were better suppressed by capivasertib than by alpelisib over a dose range. Addition of the PI3Kβ/δ inhibitor AZD8186 to alpelisib markedly enhanced the inhibition of P-AKT, P-PRAS40 and P-Sin, suggesting inhibition of PI3Kα is inadequate to block the adaptive response to palbociclib in these cells. Mean CI values showed that the combination of palbociclib/capivasertib was more synergistic against LAR TNBC cells compared to palbociclib/alpelisib (mean CI, 0.29 vs. 0.78). ARE reporter activity did not change upon inhibition of PI3K or AKT with alpelisib or capivasertib, respectively. Conclusions: Our results suggest that addition of an AKT inhibitor to palbociclib suppresses the rebound activation of AKT following treatment with the CDK4/6i and is effective in LAR TNBC with wild type Rb. In vivo studies are underway to investigate the antitumor activity of the combination of palbociclib and capivasertib in LAR TNBC xenografts. Citation Format: Gun Min Kim, Kyung-min Lee, Dhivya Sudhan, Albert Lin, Arnaldo Marin, Sumanta Chatterjee, Dan Ye, Vishal Kandagatla, Saurabh Mendiratta, Ariella Hanker, Carlos Arteaga. Combined inhibition of CDK4/6 and AKT is effective in Rb-intact triple-negative breast cancer of the luminal androgen receptor (LAR) subtype [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr PD3-07.