The AKT inhibitor capivasertib has demonstrated clinical benefit in combination with the selective ER degrader fulvestrant in PIK3CA, PTEN and AKT-1 altered estrogen receptor positive breast cancer (ER+ BC). A genome-wide CRISPR screen was performed in PI3K-AKT pathway altered ER+ BC cells exploring modifiers of response to capivasertib which identified different resistance and sensitivity drivers. Loss of chromatin regulators including KDM5C and KAT6A increased sensitivity to capivasertib. Genetic knockout or pharmacological inhibition of KDM5C strongly enhanced the anti-proliferative effects of capivasertib monotherapy, as well as in combination with fulvestrant in treatment naïve and endocrine therapy or capivasertib resistant ER+ BC cell lines. RNA-seq and epigenetic profiling revealed that combining capivasertib with KDM5C KO had a modest effect on gene transcription, with some effect on cell cycle related genes and ER signalling. In contrast, combining capivasertib with fulvestrant enhanced the effects of fulvestrant on transcriptional output and promoter occupancy. Rather than influencing gene expression, loss of KDM5C combined with capivasertib increased cell stress, DNA damage, cell cycle arrest and cell death. Collectively the data suggests that chromatin regulators may have different functions following capivasertib treatment, with inhibition having potential to enhance sensitivity to capivasertib in PIK3CA, PTEN and AKT-1 altered ER+ BC cells.

Abstract Background: PTEN loss in prostate cancer activates PI3K/AKT/mTOR signaling, driving extensive tumor microenvironment (TME) remodeling characterized by stromal desmoplasia, angiogenesis, and immune suppression. Capivasertib (AZD5363), a potent pan-AKT inhibitor, has shown therapeutic benefit in PTEN-deficient tumors when combined with androgen deprivation therapy (ADT) and abiraterone, as demonstrated in preclinical studies and the Phase III CAPItello-281 trial. Objective: To investigate how AKT inhibition modulates TME dysregulation in PTEN-deficient prostate cancer following AR-targeted therapy. Methods: Conditional Pten-knockout mouse tumors underwent baseline transcriptomic profiling to characterize AKT-driven changes and ADT effects. TME responses were evaluated in conditional Pten/Trp53 knockout mice after four weeks of ADT and abiraterone (Abi), with or without capivasertib. Analyses included qRT-PCR panels, flow cytometry, and quantitative immunohistochemistry (IHC). Results: PTEN deletion induced AKT hyperactivation and upregulated MSigDB hallmark pathways associated with TME remodeling, including hypoxia, angiogenesis, inflammatory response, IL6-STAT3, and TGFβ signaling. ADT amplified these changes, while abiraterone further increased extracellular matrix (ECM) remodeling gene expression. Capivasertib co-treatment significantly downregulated ECM and angiogenesis-related genes. Histological evaluation revealed reduced dense, haphazard collagen deposition and fewer inflammatory infiltrates in capivasertib-treated tumors. IHC confirmed decreased stromal p-S6 and p-PRAS40, lower Ki67-positive stromal cell counts, and reduced microvessel density (CD31). Gene signatures for PMN cells, MDSCs, and TAMs—key mediators of ECM remodeling—were diminished, particularly in mice showing strong antitumor responses to capivasertib. Flow cytometry and IHC corroborated the reduction of PMN/MDSC populations in treated tumors. Conclusion: Capivasertib enhances tumor growth inhibition achieved by ADT plus abiraterone and mitigates TME remodeling associated with PTEN loss and AR-targeted therapy. These findings highlight AKT inhibition as a strategy to counteract TME-driven disease progression and improve therapeutic outcomes. Citation Format: Marco A. De Velasco, Kazuko Sakai, Daiki Nakatsu, Mamoru Hashimoto, Saizo Fujimoto, Shingo Toyoda, Takafumi Minami, Kazuhiro Yoshimura, Simon T. Barry, Cath Eberlein, Claire Rooney, Kazuto Nishio, Hirotsugu Uemura, Kazutoshi Fujita. AKT inhibition with capivasertib counteracts tumor microenvironment remodeling and enhances AR-targeted therapy in PTEN-deficient prostate cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 1 (Regular Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(7 Suppl):Abstract nr 7170.

Abstract Background: PTEN-deficient prostate tumors have poor prognosis and limited response to AR-targeted therapies. PI3K/AKT activation compensates for AR inhibition, reducing the efficacy of androgen deprivation therapy (ADT) and agents such as abiraterone (Abi). Capivasertib (Capiva, AZD5363), a potent pan-AKT inhibitor, is the first to demonstrate clinical benefit when combined with Abi and ADT in PTEN-deficient metastatic hormone-sensitive prostate cancer (HSPC), as shown in the Phase 3 CAPItello-281 trial. Objective: To investigate biological responses and therapeutic outcomes of AKT inhibition with capivasertib plus AR-targeted therapy in HSPC using an integrative approach with a clinically relevant PTEN-deficient mouse model, enabling simultaneous assessment of cancer cell signaling and the tumor microenvironment. Methods: Gene expression profiling, quantitative immunohistochemistry, and flow cytometry were combined with computational analysis to characterize molecular responses to ADT (A, n=13), ADT plus abiraterone (AA, n=14), and ADT plus Abi with Capiva (AAC, n=15) in an aged PTEN-deficient mouse model of locally invasive prostate adenocarcinoma. Treatment response was classified by tumor burden (TB) relative to the population median: ≥20%, high TB; <20% and >-20%, moderate TB; ≤-20%, low TB—serving as surrogates for progressive disease, stable disease, and partial response. Progressive disease was considered unfavorable; stable disease and partial response were favorable. Results: Favorable outcomes occurred in 8/13 (61.5%), 7/14 (50%), and 12/15 (80%) of A, AA, and AAC groups. Approximately 70 markers related to signal transduction, AR signaling, DNA damage, epigenetic regulation, proliferation/apoptosis, angiogenesis, and immune composition were analyzed. Unfavorable AA outcomes correlated with high AKT signaling, PMN accumulation, and vascularization. AAC favorable responders showed sustained AKT inhibition, increased DNA damage, and reduced PMN infiltration; poor responders exhibited persistent AR signaling. Conclusion: Capiva improved response to ADT and Abi in PTEN-deficient prostate cancer. Favorable outcomes were associated with sustained AKT inhibition, reduced pro-tumor immune infiltration, and decreased vascularization. These findings underscore the importance of targeting PI3K/AKT to overcome AR therapy resistance and highlight the value of integrative approaches for biomarker discovery and optimizing therapeutic outcomes. Citation Format: Marco A. De Velasco, Kazuko Sakai, Daiki Nakatsu, Takafumi Minami, Mamoru Hashimoto, Shingo Toyoda, Saizo Fujimoto, Kazuhiro Yoshimura, Simon T. Barry, Cath Eberlein, Claire Rooney, Kazuto Nishio, Hirotsugu Uemura, Kazutoshi Fujita. Integrative analysis of capivasertib mediated AKT blockade with AR inhibition in mouse PTEN-deficient prostate cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 1 (Regular Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(7 Suppl):Abstract nr 371.

Functional loss of the tumor suppressor phosphatase and tensin homolog (PTEN) is detected in ∼40–60% of advanced prostate cancers and is linked to hyperactivation of the PI3K/AKT pathway, therapeutic resistance, and disease progression. However, most existing PTEN-deficient models lack androgen receptor (AR) expression, limiting investigation of the AR-AKT signaling interplay. We generated and characterized a novel CRISPR/Cas9-mediated PTEN knockout (KO) CWR-R1 model that retains functional AR signaling in both enzalutamide-sensitive (Parental/Par) and enzalutamide-resistant (EnzR) contexts. WGS, RNA-seq and Western blot validation confirmed complete PTEN loss and enrichment of PI3K/AKT signatures. PTEN deficiency increased phosphorylation of AKT (Ser473), S6 kinase and GSK-3β, consistent with constitutive pathway activation. Drug sensitivity profiling using the AKT inhibitor AZD5363 (Capivasertib) demonstrated a dose-dependent reduction in cell viability across all PTEN KO clones, with IC50 values markedly lower than WT controls (Par WT: 0.66 μM vs. KO clones: 0.18–0.50 μM; EnzR WT: >10 μM vs. KO clones: 0.11–0.53 μM), indicating enhanced pathway dependence. In contrast, PTEN loss modulated AR-targeted therapy response in a context-dependent manner: while Par KO clones displayed stable or reduced response to AR antagonists, EnzR KO clones exhibited partial re-sensitization, suggesting adaptive AR-AKT feedback regulation under PTEN-deficient conditions. Collectively, these findings establish the first AR-expressing CWR-R1 PTEN-KO system to dissect AR–AKT crosstalk under clinically relevant resistance settings. These findings reveal that PTEN loss enhances AKT pathway dependence and alters AR inhibitor responsiveness, supporting rational dual-pathway therapeutic strategies in PTEN-deficient prostate cancer. Shauna McClelland, Cristina Branco, Simon T. Barry, Cath Eberlein, Melissa J. LaBonte-Wilson. Functional PTEN loss rewires AR-AKT crosstalk and alters therapeutic response in a novel AR-positive prostate cancer model [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Innovations in Prostate Cancer Research and Treatment; 2026 Jan 20-22; Philadelphia PA. Philadelphia (PA): AACR; Cancer Res 2026;86(2_Suppl):Abstract nr A043.

Breast cancer is one of the most common cancers worldwide, and around 80% of breast cancers are oestrogen receptor positive (ER+ BC). For patients with ER+ advanced BC with one or more PIK3CA/AKT1/PTEN tumor alterations, capivasertib (AKT inhibitor) in combination with fulvestrant (selective oestrogen receptor (ER) degrader) is a recommended treatment. An innate PI3K/AKT pathway inhibitor resistance can occur in patients with ER+ BC, limiting their efficacy. Therefore, novel therapeutic strategies are needed to increase sensitivity to treatments in patients with ER+ BC. With this aim, from CRISPR-based sensitization screens in ER+ BC cells, we have found that the effectiveness of the AKT inhibitor capivasertib is improved by targeting the epigenetic regulators, KDM5C (lysine demethylase 5C) or KAT6A (lysine acetyltransferase 6A). Knockout (KO) of KDM5C or KAT6A strongly enhances the response to capivasertib monotherapy and its treatment in combination with fulvestrant in PIK3CA-mut and PTEN-null ER+ BC cells, as well as re-sensitizes capivasertib-resistant ER+ BC cells. Importantly, the effects of the genetic KO were recapitulated with a pan-KDM5 inhibitor and a selective KAT6A/B inhibitor in combination with capivasertib in ER+BC cells, suggesting that combination therapies, consisting of capivasertib with KDM5 or KAT6A inhibitors, could be beneficial in patients. Moreover, transcriptomic analysis and chromatin profiling techniques show that both KDM5C and KAT6A KO downregulate expression and alter chromatic accessibility of a subset of ER-target genes and this phenotype is enhanced in combination with capivasertib, suggesting that targeting KDM5C or KAT6A sensitizes cells to AKTi through a novel epigenetic regulation of ER-signaling. Also, this study reports for the first time a landscape of epigenetic differences upon capivasertib monotherapy treatment and in combination with fulvestrant in ER+BC cells, revealing changes in chromatin accessibility as a consequence of treatment with AKTi and the ER degrader. This suggests that epigenetic remodelling can lead to resistance to capivasertib and fulvestrant therapy in cancer cells. In summary, this findings identified and validated KDM5C and KAT6A as novel epigenetic targets, the inhibition of which enhances efficacy of AKTi in PI3K pathway mutated ER+ breast cancer. Inhibitors of KDM5C and KAT6A may be potential combination partners for capivasertib in ER+ breast cancer. Valentina Cutano, Shanade Dunn, Lorna Hopcroft, Eleanor M. Wigmore, Lambert Montava Garriga, Sungmi Park-Chouinard, Wu Qing, Lee Hyung Joo, Cath Eberlein, Michele Chirichella, Daniel Barrell, Toby Gurran, Omid Tavana, Neeraj Aryal, Jerome T. Mettetal, Huayang Liu, Ho Man Chan, Susan E. Critchlow, Ultan McDermott, Simon T. Barry. The epigenetic regulators KDM5C and KAT6A influence AKT inhibitor response in ER positive breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 3007.

Loss of PTEN expression, via homozygous or hemizygous deletion, is common in PIK3CA mutant ER + BC tumors. We assessed reduction of PTEN protein expression on AKT inhibitor capivasertib efficacy in PIK3CA altered tumors. In PIK3CA altered, PTEN protein high models, PI3Kα and AKT inhibition was effective, however ablation and partial PTEN expression reduction attenuated PI3Kαi but not AKTi efficacy, alone or combined with fulvestrant. Efficacy was FOXO3 dependent and associated with FOXM1 downregulation. FOXO3A deletion reduced response to capivasertib, and increased FOXM1 expression. Long term capivasertib exposure of ER+ BC cells upregulated FOXM1 expression. Downregulating FOXM1 expression reversed resistance to capivasertib, while FOXM1 overexpression reduced capivasertib efficacy. Collectively this suggests the AKT-FOXO3-FOXM1 axis plays a pivotal role in response to AKTi in ER+ breast cancer with PIK3CA mutations with and without expression of PTEN, that FOXO3 expression loss can mediate resistance, and that FOXM1 downregulation is a potential biomarker of response.

Combining fulvestrant (a selective estrogen receptor (ER) degrader) with the PI3K-AKT signalling inhibitors such as alpelisib (PI3Kα inhibitor) or capivasertib (AKT inhibitor) gives benefit to patients with ER+ breast cancer (ER+ BC) harboring PIK3CA mutations (alpelisib) and PIK3CA, PTEN and AKT-1 altered tumors (capivasertib). While PIK3CA mutations are common, PI3K-AKT signalling activation can also occur due to other alterations, including in PTEN or AKT-1, which alter pathway function and dependency. Deletion of PTEN, leading to ablation of PTEN protein, attenuates the effectiveness of PI3Kα inhibition in PIK3CA altered tumors. Our study demonstrates that in ER+ BC tumors with PIK3CA activating mutations, co-occurring PTEN homozygous or hemizygous loss is common. This study evaluates the impact of reduced PTEN protein expression on the efficacy of AKT inhibition with capivasertib in the presence of PIK3CA mutations. In PIK3CA altered and intact PTEN protein, in vivo tumor and in vitro cell line models, PI3Kα and AKT inhibitors are equally effective. However, in in vivo and in vitro PIK3CA altered models, reduction in PTEN protein expression reduces the effectiveness of PI3Kα inhibition alone and in combination with fulvestrant, while AKT inhibition remains effective. The anti-tumor activity of both monotherapy and combination treatment with PI3Kα or AKT inhibitors is associated with a decrease in FOXM1 protein and FOXM1-mediated gene expression. The regulation of FOXM1 expression is FOXO3-dependent and is directly related to the ability of the PI3Kαi or AKTi to reduce AKT dependent downstream signalling. When FOXO3a is deleted from PTEN deleted - T47D and MCF7 cells, treatment with capivasertib did not reduce FOXM1 expression. Indeed, FOXO3a loss leads to an increase in FOXM1 expression, resulting in no impact on cell viability despite the presence of capivasertib. These findings indicate that inhibiting AKT signalling is a more effective strategy than targeting PI3Kα to address this crucial effector node across a heterogeneous array of PI3K-AKT tumor drivers. Furthermore, the study highlights the pivotal role of the AKT-FOXO3-FOXM1 axis in mediating responses to AKT inhibitors in ER+ breast cancer with PIK3CA mutations regardless of PTEN expression. In addition, loss of FOXO3a expression can mediate resistance, and FOXM1 downregulation serves as a crucial biomarker of response to the combination treatment. Valentina Cutano, Ming Li Chia,Eleanor M. Wigmore, Stuart C. Williamson, Amanda L. Christie, Brandon Willis, James Kerr, Sophie D’Arcy, Lauren Bradshaw, Cath Eberlein, Lambert Montava Garriga, Elza de Bruin, Susan E. Critchlow, Kevin M. Brindle, Simon T Barry, Susana Ros. The interplay between FOXO3 and FOXM1 influences sensitivity to AKT inhibition in PIK3CA and PIK3CA/PTEN altered estrogen receptor positive breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 3008.

Inhibition of the androgen receptor (AR) is the primary treatment for metastatic hormone-sensitive prostate cancer (mHSPC). The addition of antiandrogen therapies to androgen deprivation therapy (ADT) has greatly improved patient outcomes. However, loss of the tumor suppressor PTEN is common in prostate cancer (PCa), and the resulting increase in AKT signaling contributes to PCa progression. Capivasertib (AZD5363) is currently being investigated as an oral pan-AKT inhibitor in combination with abiraterone (Abi) and ADT for treating mHSPC in patients with PTEN loss (CAPItello-281). We previously demonstrated the efficacy of targeted AKT inhibition using capivasertib in preclinical mouse models of PTEN-deficient PCa (PMID: 26910118). In this study, we evaluated the antitumor and molecular responses to the combination of Abi and capivasertib in vivo using conditional knockout mouse models with targeted deletions of Pten (KO) and both Pten and Trp53 (DKO). In DKO mice, four weeks of ADT (via surgical castration) followed by four weeks of Abi resulted in a 9.4% tumor growth inhibition (TGI) compared to ADT alone. Additionally, 3/8 (37.5%) mice treated with Abi had tumor burden reductions >20% compared to ADT alone. In a hormone-sensitive model using DKO mice, four-week treatment with ADT/Abi resulted in a 7.4% TGI based on genitourinary tract weight compared with ADT alone. The combination of ADT and Abi+capivasertib further improved the TGI to 21.8%. DKO mice with advanced PCa also exhibited improved antitumor activity with the combination of ADT/Abi+capivasertib compared with ADT/Abi. In survival studies involving DKO mice with advanced PCa, the addition of capivasertib to ADT/Abi reduced metastasis, extended tumor doubling time, and improved OS compared with ADT/Abi alone. Immunohistochemical analysis revealed that mice treated with ADT/Abi+capivasertib exhibited significantly lower proliferation and increased apoptotic rates. Molecular profiling studies revealed that mice treated with Abi exhibited increased AKT signaling, as indicated by increased PRAS40 and S6 phosphorylation, but this enhancement was inhibited by capivasertib. Syngeneic allograft transplantation models using PTEN-expressing TRAMP-C1 and Pten-null-derived PCa cells demonstrated that, while both models responded to capivasertib, the Pten-null allografts exhibited greater sensitivity to the ADT/Abi+capivasertib combination. In conclusion, we provide preclinical evidence that abiraterone-resistant tumors with hyperactivation of AKT due to loss of PTEN are sensitive to AKT inhibition. Marco A. De Velasco, Yurie Kura, Kazuko Sakai, Simon T. Barry, Cath Eberlein, Claire Rooney, Kazuto Nishio, Kazutoshi Fujita, Hirotsugu Uemura. Evaluation of antitumor and molecular responses to abiraterone acetate plus capivasertib in mouse PTEN-deficient prostate cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 1685.

Taxane chemotherapy is the standard treatment for metastatic castration-resistant prostate cancer (mCRPC). The tumor suppressor PTEN is frequently deleted in advanced prostate cancer (PCa), contributing to cancer progression and poor clinical outcomes. Hyperactivation of AKT resulting from PTEN loss and reciprocal crosstalk between AR and PI3K/AKT signaling may impair the efficacy of taxane therapy. Capivasertib (AZD5363) is a potent oral pan-AKT inhibitor that has shown efficacy against PCa in preclinical and early phase clinical studies. Capivasertib is currently being evaluated in a Phase 3 trial (CAPItello-280) along with docetaxel (Dtx) for the treatment of patients with mCRPC. Here, we assessed the in vivo preclinical efficacy of Dtx plus capivasertib using transgenic mouse models of Pten-null PCa. In an early-stage model of PCa using double knockout mice with conditional inactivation of Pten and Trp53, four weeks of treatment with Dtx resulted in tumor growth inhibition (TGI) of approximately 25% and 7% compared with vehicle-treated control mice in hormone-sensitive PCa (HSPC) and CRPC settings, respectively. Adding capivasertib to Dtx further increased tumor TGI by ∼14% in both settings. More robust improvements were observed with the combination therapy in CRPC compared with HSPC. Namely, 7/10 (70%) and 9/10 (90%) of HSPC mice treated with Dtx and Dtx+capivasertib, respectively, exhibited a >25% reduction relative to the control group. In contrast, 2/15 (13.3%) and 8/18 (44.4%) of CRPC mice treated with Dtx and Dtx+capivasertib, respectively, showed similar reductions. After one week of treatment, capivasertib suppressed the phosphorylation of PRAS40 and S6 downstream molecules of AKT, and this suppression was sustained for four weeks. In HSPC, Dtx+capivasertib resulted in a greater decrease in cancer cell proliferation compared with DTx alone and control mice. One week of administration of Dtx with or without capivasertib in CRPC mice increased cleaved caspase-3 levels to levels higher than those in control mice, whereas both Ki67 and cleaved caspase-3 levels plateaued in atrophic acini during week four suggesting M-phase cell cycle arrest. The therapeutic benefits of Dtx+ capivasertib were further evaluated in a late-stage CRPC model. Mice with tumors treated with Dtx+ capivasertib after progression to androgen deprivation therapy (surgical castration) and apalutamide had longer survival and longer tumor doubling times than those treated with Dtx alone. In conclusion, PTEN-deficient CRPC is less sensitive to Dtx than HSPC. However, our model showed that adding capivasertib to Dtx suppressed tumor growth and improved the therapeutic efficacy of CRPC. Marco A. De Velasco, Yurie Kura, Kazuko Sakai, Simon T. Barry, Cath Eberlein, Claire Rooney, Kazuto Nishio, Kazutoshi Fujita, Hirotsugu Uemura. Enhancing chemotherapy efficacy in PTEN-deficient prostate tumors with targeted AKT inhibition [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 1686.

Background/objective To explore the anti-tumour activity of combining AKT inhibition and docetaxel in PTEN protein null and WT prostate tumours. Methods Mechanisms associated with docetaxel capivasertib treatment activity in prostate cancer were examined using a panel of in vivo tumour models and cell lines. Results Combining docetaxel and capivasertib had increased activity in PTEN null and WT prostate tumour models in vivo. In vitro short-term docetaxel treatment caused cell cycle arrest in the majority of cells. However, a sub-population of docetaxel-persister cells did not undergo G2/M arrest but upregulated phosphorylation of PI3K/AKT pathway effectors GSK3β, p70S6K, 4E-BP1, but to a lesser extent AKT. In vivo acute docetaxel treatment induced p70S6K and 4E-BP1 phosphorylation. Treating PTEN null and WT docetaxel-persister cells with capivasertib reduced PI3K/AKT pathway activation and cell cycle progression. In vitro and in vivo it reduced proliferation and increased apoptosis or DNA damage though effects were more marked in PTEN null cells. Docetaxel-persister cells were partly reliant on GSK3β as a GSK3β inhibitor AZD2858 reversed capivasertib-induced apoptosis and DNA damage. Conclusion Capivasertib can enhance anti-tumour effects of docetaxel by targeting residual docetaxel-persister cells, independent of PTEN status, to induce apoptosis and DNA damage in part through GSK3β.

Overactivation of the PI3K/AKT pathway can occur in many cancers. Capivasertib is a potent, selective pan-AKT inhibitor. The objectives of this analysis were to develop a population pharmacokinetic model for capivasertib and to quantitatively assess the impact of intrinsic and extrinsic factors on the pharmacokinetics of capivasertib. Pharmacokinetic data from four phase I and II studies were combined. Capivasertib was administered orally at a dose range of 80–800 mg twice daily over 28-day and 21-day cycles as monotherapy or in combination with paclitaxel or fulvestrant, using continuous dosing or one of two intermittent dosing schedules: either 4 days on, 3 days off (4/3) or 2 days on, 5 days off (2/5). Several models and approaches were tested for their ability to describe capivasertib disposition. The covariates assessed included dose, schedule, age, body weight, race, sex, creatinine clearance, hepatic function, renal function, smoking status, food effect, formulation, and concomitant use with paclitaxel, fulvestrant, cytochrome P450, family 3, subfamily A (CYP3A) inducers, CYP3A inhibitors and acid-reducing agents. A total of 3963 capivasertib plasma concentrations from 441 patients were included. Capivasertib pharmacokinetics was adequately described by a three-compartment model where the apparent clearance (CL/F) presented a moderate time-dependent and dose-dependent clearance. Following oral administration of multiple doses of capivasertib (400 mg twice daily; [4/3]), the initial CL/F was 62.2 L/h (between-subject variability 39.3

This review delves into the intricate roles of interleukin-8 (IL-8) and its receptors, CXCR1 and CXCR2, in prostate cancer (PCa), particularly in castration-resistant (CRPC) and metastatic CRPC (mCRPC). This review emphasizes the crucial role of the tumour microenvironment (TME) and inflammatory cytokines in promoting tumour progression and response to tumour cell targeting agents. IL-8, acting through C-X-C chemokine receptor type 1 (CXCR1) and type 2 (CXCR2), modulates multiple signalling pathways, enhancing the angiogenesis, proliferation, and migration of cancer cells. This review highlights the shift in PCa research focus from solely tumour cells to the non-cancer-cell components, including vascular endothelial cells, the extracellular matrix, immune cells, and the dynamic interactions within the TME. The immunosuppressive nature of the PCa TME significantly influences tumour progression and resistance to emerging therapies. Current treatment modalities, including androgen deprivation therapy and chemotherapeutics, encounter persistent resistance and are complicated by prostate cancer’s notably “immune-cold” nature, which limits immune system response to the tumour. These challenges underscore the critical need for novel approaches that both overcome resistance and enhance immune engagement within the TME. The therapeutic potential of inhibiting IL-8 signalling is explored, with studies showing enhanced sensitivity of PCa cells to treatments, including radiation and androgen receptor inhibitors. Clinical trials, such as the ACE trial, demonstrate the efficacy of combining CXCR2 inhibitors with existing treatments, offering significant benefits, especially for patients with resistant PCa. This review also addresses the challenges in targeting cytokines and chemokines, noting the complexity of the TME and the need for precision in therapeutic targeting to avoid side effects and optimize outcomes.

Capivasertib is a potent, selective inhibitor of all 3 Akt isoforms (Akt1/2/3), and it is currently being tested in Phase III trials for the treatment of prostate and breast cancer. To investigate the effect of a cytochrome P450 3A4 (CYP3A4) inhibitor on the pharmacokinetics of capivasertib, a Phase I drug-drug interaction study of capivasertib and itraconazole was conducted in 11 healthy volunteers (median age, 54 years). The 8-day study had 3 stages: Participants received a single dose of capivasertib 80 mg in Stage 1, 4 doses of itraconazole 200 mg over 3 days in Stage 2, and a final dose of capivasertib 80 mg coadministered with itraconazole 200 mg in Stage 3. Capivasertib pharmacokinetics were examined in Stages 1 and 3. Itraconazole coadministration increased the maximum plasma concentration of capivasertib and total capivasertib exposure (area under the concentration-time curve from time of administration to infinity) by 1.70-fold (90% confidence interval, 1.56-1.86) and 1.95-fold (90% confidence interval, 1.82-2.10), respectively.

Supp Fig 1 Tumour efficacy Supp Fig 2 In vitro gene expression modulation Supp Fig 3 In vivo biomarker analysis Supp Fig 4 HCC70 In vivo FDG uptake imaging Supp Fig 5 U87MG in vivo FDG uptake imaging

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.

PDF file - 182KB, Pharmacokinetic analysis of AZD9291, AZ5104 and AZ7550 total plasma concentrations vs time following single oral dose of 25mg/kg AZD9291 in mice.

PDF file - 470KB, Effect of AZD9291 and AZ5104 in transgenic models of EGFR-TKI sensitizing (C/L858R and C/ex19del) and T790M resistant (C/L+T) lung cancer.

Supplementary Table 1: Cell lines; Supplementary Table 2: Antibodies; Supplementary Table 3: Gene lists

Supplementary methods for in vivo studies

PDF file - 312KB, Efficacy of AZD9291 in H3255, PC-9VanR and A431 xenograft models. Weight loss data for chronically dosed AZD9291 in PC-9 and H1975 xenograft models.