CYP17 Inhibitor Research Articles

TBCRC 058: A randomized phase II study of enzalutamide, enzalutamide with mifepristone, and treatment of physician’s choice in patients with androgen receptor-positive metastatic triple-negative or estrogen receptor-low breast cancer (NCT06099769).

TPS1138 Background: Triple-negative breast cancer (TNBC) refers to a heterogenous group of breast cancers that lack expression of ER, PR, and HER2. Despite recent advances with immunotherapy (IO) and antibody-drug conjugates (ADCs), TNBC remains the most aggressive subtype, characterized by a high risk of recurrence and a short overall survival in the metastatic setting. Breast tumors with low levels of ER and PR expression (1-10%) clinically behave like TNBC, and clinical management follows the TNBC treatment (tx) paradigm. We and others have identified a subset of ER/PR/HER2 negative breast cancers (BC) that express the androgen receptor (AR). Enzalutamide (enza), an AR-antagonist, has demonstrated activity in AR+ metastatic TNBC (Traina et al, JCO 2018). Activation of the glucocorticoid receptor (GR) has been implicated as a mechanism of resistance to AR inhibition in prostate and BCs (Kach et al, Sci Transl Med 2015). Effective therapies for advanced TNBC remain an unmet need, particularly in patients who are ineligible for or progress following a checkpoint inhibitor. This randomized study will evaluate the efficacy of enzalutamide or enzalutamide plus the GR antagonist mifepristone (mif) as compared to physician’s choice chemotherapy (TPC). Methods: This is a randomized phase II trial; 201 patients (pts) will be randomized in a 1:1:1 fashion to enza, enza with mif, or TPC (carboplatin, paclitaxel, eribulin, or capecitabine). The primary endpoint (endpt) is progression free survival (PFS), and the trial is designed to test the hypothesis that PFS in the pooled enzalutamide arms is superior to TPC; there is 80% power to detect a hazard ratio (HR) of 0.70, corresponding to increase in PFS from 3.5 months (mos) with TPC to 5.0 mos with enza-based tx. Secondary endpts include comparisons of PFS among 3 arms and evaluation of response rate, clinical benefit rate, duration of response, overall survival, safety/toxicity, and patient-reported outcomes by arm. Exploratory endpts include correlation of tumor and circulating markers (constitutively active AR variants in circulating tumor cells and circulating tumor cell DNA) with tx response. Eligible pts must have: ECOG 0-2, metastatic ER/PR low or negative, HER2 negative breast cancer (BC), measurable or evaluable disease (dz), < 2 prior lines of chemotx, any # prior endocrine txs, no prior anti-AR tx, no prior mif, concurrent CYP17 inhibitors prohibited. Pts with PD-L1+ BC must have received prior IO if not contraindicated. Tumors must have AR ≥10%, normal organ function, no history of brain mets. As of 1/15/2024, 2 of 201 pts have begun protocol-specified tx. Clinical trial information: NCT06099769 .

Synthesis and Biological Evaluation of Methoxypolyethylene-Glycol-Substituted Abiraterone Derivatives as Potential Antiprostate Cancer Agents.

Globally, prostate cancer is the most commonly diagnosed tumor and a cause of death in older men. Abiraterone, an orally administered irreversible CYP17 inhibitor, is employed to treat prostate cancer. However, abiraterone has several clinical limitations, such as poor water solubility, low dissolution rate, low bioavailability, and toxic side effects in the liver and kidney. Therefore, there is a need to identify high-efficiency and low-toxicity water-soluble abiraterone derivatives. In this work, we aimed to design and synthesize a series of abiraterone derivatives by methoxypoly(ethylene glycol) (mPEG) modification. Their antitumor activities and toxicology were analyzed in vitro and in vivo. The most potent compound, 2e, retained the principle of action on the CYP17 enzyme target and significantly improved the abiraterone water solubility, cell permeability, and blood safety. No significant abnormalities were observed in toxicology. mPEG-modification significantly improved abiraterone's antitumor activity and efficiency while reducing the associated toxic effects. The finding will provide a theoretical basis for future clinical application of mPEG-modified abiraterone.

Abstract 7277: Discovery of INV-9956, an orally available and highly selective Cyp11A1 inhibitor for the treatment of castration-resistant prostate cancer with drug resistant AR mutations

Abstract Androgen Receptor (AR) signaling plays a profound role in prostate cancer and development. Efforts in harnessing androgen and AR axis for castration-resistant prostate cancer treatment have led to discovery of several therapeutics, including AR antagonists and Cyp17 inhibitors. However, resistance to these approved therapeutics has emerged, and remained a significant unmet medical need. Among the prominent resistance mechanisms of action are restored androgen signaling via AR amplification and overexpression, and gain-of-function mutations occurring at AR ligand binding domain that can be agonized by existing AR antagonists and/or non-androgenic steroids such as glucocorticoids. Targeting Cyp11A1 that catalyzes the formation of pregnenolone is effective to ablate biosynthesis of androgens and all steroids and thus holds promise to deliver coverage of a significant percentage of drug resistant AR mutations and benefit CRPC patients post treatment with AR antagonists or Cyp17 inhibitors. Here we present discovery and characterization of INV-9956, an orally available, selective, and potent Cyp11A1 inhibitor with well-acceptable pharmacokinetic properties. INV-9956 potently inhibits biosynthesis of pregnenolone and other androgens in H295R cells with IC50 at single-digit nanomolar, suppresses proliferation of prostate cancer cell lines harboring major clinically acquired drug resistant AR LBD mutations, such as AR L702H using coculture assays. Orally administered INV-9956 showed consistent dose dependent PK/PD correlations across animal species. Particularly, INV-9956 displayed pronounced tumor inhibition superior to known competitors in a CRPC VCaP xenograft model and in a “humanized” animal model. Furthermore, INV-9956 displayed a good tox profile in 14-day repeated dosing rat and dog studies, supported by a high selectivity to Cyp11A1 over other Cyp family members, clean hERG and mini-Ames, and no significant off-target activity in a safety panel screen. The promising preclinical profiles of INV-9956 lend strong support to its potentials in addressing unmet needs in CRPC treatments and warrant clinical development. Citation Format: Chang Bai, Danqi Chen, Zilei Xia, Shujuan Huang, LIshan Lin, Zhaopie Zeng, Jing Su, Yongkui Sun. Discovery of INV-9956, an orally available and highly selective Cyp11A1 inhibitor for the treatment of castration-resistant prostate cancer with drug resistant AR mutations [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 7277.

Olaparib (Lynparza)


 CADTH recommends that Lynparza, in combination with abiraterone and prednisone or prednisolone, should be reimbursed by public drug plans for the treatment of patients with metastatic castration-resistant prostate cancer (mCRPC) if certain conditions are met.
 Lynparza should only be covered to treat patients with mCRPC who have BRCA mutations, who have not been treated with an androgen receptor pathway inhibitor (ARPi), who have not been treated with a poly-(ADP ribose) polymerase (PARP) inhibitor for mCRPC, and who have not been treated with a CYP-17 inhibitor for mCRPC for more than 4 months. Also, the patients should be in relatively good health.
 Lynparza, in combination with abiraterone and prednisone or prednisolone, should only be reimbursed if it is prescribed by a clinician with expertise in treating prostate cancer with systemic anticancer therapy and if the costs of both Lynparza and abiraterone are reduced.

1064nm Nd:YAG laser promotes chondrocytes regeneration and cartilage reshaping by upregulating local estrogen levels.

Cartilage is frequently used as a scaffolds for repairing and reconstructing body surface organs. However, after successful plastic surgery, transplanted cartilage scaffolds often exhibit deformation and absorption over time. To enhance the shaping stability of cartilage scaffolds and improve patients' satisfaction after reconstructions, we employed the ear folding models in New Zealand rabbits to confirm whether the 1064nm neodymium-doped yttrium aluminum garnet (Nd:YAG) laser could promote cartilage reshaping. There was an increase in collagen and aromatase (Cyp19) expression within the ear cartilage after laser treatment. Moreover, we have found that the Cyp19 inhibitor can inhibit the laser's effect on cartilage shaping and reduce collagen and Cyp19 expression. The overall findings suggest that treatment with 1064nm Nd:YAG laser irradiation can enhance estrogen levels in local cartilage tissues by upregulating Cyp19 expression in chondrocytes through photobiomodulation, thereby promoting the proliferation and collagen secretion of chondrocytes to improve cartilage reshaping and stability.

Cortisol as Biomarker for CYP17-Inhibition is Associated with Therapy Outcome of Abiraterone Acetate.

Abiraterone acetate is an irreversible 17α-hydroxylase/C17, 20-lyase (CYP17) inhibitor approved for the treatment of metastatic castration-resistant prostate cancer (mCRPC) patients. Inhibition of this enzyme leads to low testosterone and cortisol levels in blood. There is growing evidence that clinical efficacy of abiraterone is related to the rate of suppression of serum testosterone. However, quantification of very low levels of circulating testosterone is challenging. We therefore aimed to investigate whether circulating cortisol levels could be used as a surrogate biomarker for CYP17 inhibition in patients with mCRPC treated with abiraterone acetate. mCRPC patients treated with abiraterone acetate were included. Abiraterone and cortisol levels were measured with a validated liquid chromatography-tandem mass spectrometry (LC-MS/MS). On treatment cortisol and abiraterone concentrations were related to treatment response and progression free survival. In total 117 patients were included with a median cortisol concentration of 1.13ng/ml (range: 0.03 - 82.2) and median abiraterone trough concentration (Cmin) of 10.2ng/ml (range: 0.58 - 92.1). In the survival analyses, abiraterone Cmin ≥ 8.4ng/mL and cortisol < 2.24ng/mL were associated with a longer prostate-specific antigen (PSA) independent progression-free survival than patients with an abiraterone concentration ≥ 8.4ng/mL and a cortisol concentration ≥ 2.24ng/mL (13.8months vs. 3.7months). Our study shows that cortisol is not an independent predictor of abiraterone response in patients with mCRPC, but it is of added value in combination with abiraterone levels, to predict a response on abiraterone.

FRI242 Primary And Secondary Adrenal Insufficiency Post Transsphenoidal Surgery In Patient On Abiraterone Therapy

Abstract Disclosure: R.O. Akande: None. J. Abramowitz: None. S. Mirfakhraee: None. Introduction: This case report describes the co-existence of primary and secondary adrenal insufficiency in a patient who received abiraterone therapy for metastatic prostate cancer and had transsphenoidal surgery for symptomatic pituitary adenoma. It sheds light on the presentation of the patient and explains the subsequent management. Clinical Case: A 67-year-old man with a history of metastatic prostate cancer (status post prostatectomy and radiation) and recent transsphenoidal surgery for pituitary adenoma presented with 3+ pedal edema. The patient had been discharged on hydrocortisone as per neurosurgery protocol and continued abiraterone after his transsphenoidal surgery. His pedal edema started two months after discharge. He denied fatigue, nausea, and dizziness. His vital signs and electrolytes, including serum potassium, were within normal limits. The patient was diagnosed with mineralocorticoid excess in the context of combined primary and secondary adrenal insufficiency. His hydrocortisone was changed to prednisone 5mg daily and his pedal edema subsequently resolved. Conclusion: Abiraterone, a hormonal therapy for the treatment of metastatic prostate cancer, is an irreversible inhibitor of CYP17, a microsomal enzyme with 17 alpha-hydroxylase and 17,20-lyase activities. This inhibition reduces cortisol and androgen concentrations while stimulating ACTH production. Thus, abiraterone use led to primary adrenal insufficiency in this patient. As a result of the 17 alpha-hydroxylase and 17,20-lyase pathway inhibition, there is increased production of deoxycorticosterone, which can lead to fluid retention. This patient was post pituitary surgery with partial secondary adrenal insufficiency and received hydrocortisone postoperatively as an appropriate glucocorticoid replacement in this setting. He developed pedal edema due to mineralocorticoid excess from abiraterone use while on hydrocortisone therapy. He was placed on prednisone, a more potent synthetic glucocorticoid than hydrocortisone, with subsequent rapid resolution of his edema. Presentation: Friday, June 16, 2023

Baseline circulating tumor cell (CTC) count as a prognostic marker of overall survival (OS) in metastatic hormone sensitive prostate cancer (mHSPC): Results from SWOG S1216, a phase III randomized trial of androgen deprivation plus orteronel (cyp17 inhibitor) or bicalutamide.

5080 Background: Biomarkers are needed to predict clinical outcomes in mHSPC. We previously reported that baseline CTC counts in S1216 were prognostic of PSA response and disease progression ( ASCO 2020; CCR 2021). However, the trial’s primary overall survival (OS) endpoint was not yet mature at that time. Here we present the final results of S1216 using all available samples to assess the prognostic value of CTC counts for response, progression, OS, and treatment arm interactions. Methods: In S1216, peripheral blood was drawn with informed consent at registration (baseline) and at progression to metastatic castrate resistant prostate cancer (mCRPC). CTCs were enumerated on the FDA-cleared CellSearch platform (Menarini). CTC counts were evaluated for associations with 3 pre-specified trial endpoints: 7-month PSA (7mPSA) ≤ 0.2 ng/ml vs. 0.2–4.0 vs. &gt; 4.0 using a generalized logit model; and progression-free survival (PFS) and OS using Cox regression. Results: From 2014 to 2021, 503 evaluable samples were collected at baseline and 93 at progression. Baseline CTC count was ≥5 in 11.9% of samples, 1-4 in 19.3%, and 0 in 66.8%. Comparing men with 0 vs. ≥5 CTCs at baseline, those with 0 CTCs were significantly more likely to attain a complete PSA response and had significantly lower risk of a PFS event and death after adjusting for clinical covariates (disease burden, bone metastases, age, race, alkaline phosphatase, hemoglobin, PSA, treatment arm). These associations were not modified by treatment arm. Progression CTCs &lt;5 vs. ≥5 also were prognostic of OS (logrank p=0.001), consistent with prior findings in mCRPC. Same-patient CTC counts in matched baseline-progression pairs (n=61) were highly correlated (Spearman p&lt;0.001). Conclusions: CTC count at the start of treatment for mHSPC was highly prognostic of PSA response, PFS, and OS; associations that held in both treatment arms. Moreover, baseline CTC count strongly correlated with progression count, suggesting that mild vs. aggressive disease phenotypes may persist from mHSPC to mCRPC. This evidence from a large prospective phase 3 trial suggests that baseline CTC count is a valuable prognostic marker in men initiating therapy for mHSPC, discriminating those likely to experience favorable vs. unfavorable response and OS. [Table: see text]

Steroidogenesis in castration-resistant prostate cancer.

Castration resistance is in part attributable to aberrant activation of androgen receptor (AR) signaling by the intracrine activation of androgen precursors derived from adrenal glands. To overcome this, novel AR pathway inhibitors (ARPIs) that suppress androgen synthesis by CYP17 inhibition or AR activation by antiandrogen effects have been developed. However, primary or acquired resistance to these ARPIs occurs; in turn attributable, at least in part, to the maintained androgen milieu despite intensive suppression of AR signaling similar to castration resistance. In addition to the classical pathway to produce potent androgens such as testosterone and dihydrotestosterone, the alternative pathway and the backdoor pathway which bypasses testosterone to produce dihydrotestosterone have been shown to play a role in intratumor steroidogenesis. Furthermore, the 11β-hydroxyandrostenedione pathway to produce the potent oxygenated androgens 11-ketotestosterone and 11-ketodihydrotestosterone has been suggested to be functional in prostate cancer. These steroidogenesis pathways produce potent androgens that promote tumor resistance to endocrine therapy including novel ARPIs. Here, we overview the current evidence on the pathological androgen milieu by altered metabolism and transport in prostate cancer, leading to resistance to endocrine therapy.

Bone Biomarkers and Subsequent Survival in Men with Hormone-sensitive Prostate Cancer: Results from the SWOG S1216 Phase 3 Trial of Androgen Deprivation Therapy with or Without Orteronel

BackgroundBone biomarkers are strongly prognostic for overall survival (OS) in men with castration-resistant prostate cancer but not fully established for hormone-sensitive prostate cancer (HSPC). ObjectiveBone biomarkers in HSPC were prospectively evaluated as part of a phase 3 study of androgen deprivation therapy ± the CYP17 inhibitor orteronel. Design, setting, and participantsPatients were randomly divided into training (n = 316) and validation (n = 633) sets. Recursive partitioning and Cox proportional hazard models were employed. Outcome measurements and statistical analysisBone resorption (C-telopeptide and pyridinoline) and bone formation markers (C-terminal collagen propeptide and bone alkaline phosphatase) were assessed from patient sera. Results and limitationsOf 1279 men, 949 had evaluable baseline bone biomarkers. Optimal cutoffs were identified to define elevated levels of each of the four biomarkers (all p < 0.05) that were associated with worse OS. After adjusting for clinical risk factors in the validation set, elevated bone biomarkers were statistically significantly associated with an increased risk of death (hazard ratios ranging from 1.37 to 1.92). Recursive partitioning algorithms applied to the training set identified three risk groups (low, intermediate, and poor) with differential OS outcomes (median OS: 8.2, 5.1, and 2.1 yr, respectively) based on combinations of bone biomarkers. These results were confirmed in the validation set. ConclusionsIn men with HSPC initiating androgen deprivation therapy, bone biomarkers are strongly and independently prognostic for OS. Bone biomarker levels alone or in combination with clinical covariates identify unique subsets of men with differential OS outcomes. These results validate the clinical value of bone biomarker assessment in the HSPC state, extending bone biomarker utility beyond the castration-resistant state. Patient summaryIn men with newly diagnosed metastatic prostate cancer, high levels of bone turnover biomarkers are associated with a shorter lifespan.

AOP Report: Adverse Outcome Pathways for Aromatase Inhibition or Androgen Receptor Agonism Leading to Male-Biased Sex Ratio and Population Decline in Fish.

Screening and testing of potential endocrine-disrupting chemicals for ecological effects are examples of risk assessment/regulatory activities that can employ adverse outcome pathways (AOPs) to establish linkages between readily measured alterations in endocrine function and whole organism- and population-level responses. Of particular concern are processes controlled by the hypothalamic-pituitary-gonadal/thyroidal (HPG/T) axes. However, the availability of AOPs suitable to meet this need is currently limited in terms of species and life-stage representation relative to the diversity of endpoints influenced by HPG/T function. In our report we describe two novel AOPs that comprise a simple AOP network focused on the effects of chemicals on sex differentiation during early development in fish. The first AOP (346) documents events starting with inhibition of cytochrome P450 aromatase (CYP19), resulting in decreased availability of 17β-estradiol during gonad differentiation, which increases the occurrence of testis formation, resulting in a male-biased sex ratio and consequent population-level declines. The second AOP (376) is initiated by activation of the androgen receptor (AR), also during sexual differentiation, again resulting in a male-biased sex ratio and population-level effects. Both AOPs are strongly supported by existing physiological and toxicological evidence, including numerous fish studies with model CYP19 inhibitors and AR agonists. Accordingly, AOPs 346 and 376 provide a basis for more focused screening and testing of chemicals with the potential to affect HPG function in fish during early development. Environ Toxicol Chem 2023;42:747-756. Published 2023. This article is a U.S. Government work and is in the public domain in the USA.

Real-world effectiveness of darolutamide in metastatic castration-resistant prostate cancer: Experience from a safety-net hospital serving a racially and ethnically diverse patient population.

150 Background: Androgen deprivation therapy (ADT), CYP17 inhibitors (CYP17Is, e.g., abiraterone) and 2nd generation androgen receptor (AR) antagonists (2GARAs: enzalutamide, apalutamide, darolutamide) are important treatments for advanced prostate cancer (PC). Darolutamide is FDA-approved with ADT in non-metastatic castration-resistant PC (M0-CRPC) and with ADT+docetaxel in metastatic castration-sensitive PC (M1-CSPC). However, Phase III trials evaluating darolutamide excluded patients (pts) previously treated with other 2GARAs or CYP17Is, thus clinical cross-resistance remains to be evaluated. While reported that darolutamide may be active in vitro against AR mutants resistant to enzalutamide, this also has not been examined clinically. We assessed the real-world effectiveness of darolutamide in a racially/ethnically diverse population of M1-CRPC pts with prior exposure to CYP17Is and/or other 2GARAs. Methods: With IRB approval, we abstracted clinical data from advanced PC pts receiving care at Ben Taub Hospital, a safety-net public hospital serving a racially/ethnically diverse patient population. We identified 33 M1-CRPC pts (17 non-Hispanic African American, 14 Hispanic white, 1 non-Hispanic white, 1 Asian) and 4 M0-CRPC pts (2 non-Hispanic African American, 2 Hispanic white) treated with darolutamide. Tissue and longitudinal circulating tumor DNA (ctDNA) next-generation sequencing data (Tempus Labs, Chicago, IL), including of the AR gene, were also included. Progression-free survival (PFS) was estimated with the Kaplan-Meier method. Results: Amongst the 33 M1-CRPC pts, before receiving darolutamide, 21 had progressed on CYP17Is but had not received 2GARAs; 11 had progressed on both classes of agents; and 1 had progressed on 2GARA but had not received CYP17Is. Darolutamide suppressed PSA by at least 50% in 4/33 pts (12%, all previously 2GARA-naïve). PFS at 3, 6 and 12 months was 36%, 10%, and 5%, respectively, for the entire M1-CRPC cohort; 42%, 17%, and 8% for pts with prior resistance to CYP17Is but not to 2GARA; 25%, 0% and 0% for pts with prior resistance to 2GARA; and 31%, 0% and 0% for pts with AR mutations detected before darolutamide treatment, respectively. AR mutations that emerged or increased in ctDNA allele fraction while on darolutamide included L702H, H875Y, H100Q, D891H, T878A, L329W and AR copy number gain, suggesting a possible role in darolutamide resistance. All four M0-CRPC pts (no prior CYP17I or 2GARA exposure) had PSA declines &gt;50% and remain progression-free at 12 months of treatment. Conclusions: Sequential treatment with darolutamide after progression on a CYP17I may benefit some M1-CRPC pts. However, prior resistance to enzalutamide/apalutamide and/or associated AR mutations can significantly decrease the likelihood of benefit from darolutamide.

Correlation Between Trough Level of Abiraterone and Prostate-Specific Antigen (PSA) Response in Metastatic Hormone-Sensitive Prostate Cancer.

BackgroundProstate cancer growth is primarily driven by testosterone and 5α-dihydrotestosterone. Abiraterone is an irreversible inhibitor of CYP17, and CYP17 inhibition is a required step in testosterone biosynthesis. Previous studies have shown that abiraterone trough levels are predictive of prostate-specific antigen (PSA) response in metastatic castrate-resistant prostate cancer (mCRPC). It has not been demonstrated if this association exists for patients with metastatic hormone-sensitive prostate cancer (mHSPC). In this study, we aimed to explore the correlation and association between abiraterone trough levels and PSA levels in patients with mHSPC.Material/MethodsThis was a single-center, prospective, observational study of patients with mHSPC being treated with abiraterone acetate (AA) 1000 mg once daily. Abiraterone trough levels (22–26 h after drug administration) were drawn at 1, 3, and 7 months after treatment initiation.ResultsThirteen patients with mHSPC were enrolled, and complete pharmacokinetic data were available for 8 patients. The mean trough levels at 1 month, 3 months, and 7 months were 34.49 ng/mL (3.36–240.46), 13.82 ng/mL (2.91–29.96), and 15.7 ng/mL (3.58–26.86), respectively. The correlation between the 1-month abiraterone trough level and 1-month PSA level was 0.29 (P=0.38), between 3-month abiraterone trough and 3-month PSA was −0.61 (P=0.08), and between 7-month abiraterone trough and 7-month PSA was −0.31 (P=0.54).ConclusionsThis study demonstrated a trend toward a negative correlation between 3-month abiraterone trough levels and PSA levels, but the correlation was not statistically significant. A study with a larger prospective sample size is needed to validate these findings.

A phase 1b clinical trial of cabozantinib (CABO) and abiraterone (ABI) with checkpoint inhibitor immunotherapy (CPI) in metastatic hormone-sensitive prostate cancer (mHSPC) (CABIOS Trial).

TPS214 Background: Multiple systemic therapies have resulted in improved overall survival (OS) for mHSPC, including several AR-targeted agents (ARTA) and docetaxel chemotherapy. However, patients (pts) with high volume de novo metastatic prostate cancer still only have an OS of approximately 50 months. Thus, more effective combination strategies for initial treatment of mHSPC are urgently needed. CABO, a multi-tyrosine kinase inhibitor (including MET, VEGFR-1, -2,-3, AXL) has shown synergy with ABI as well as with CPI in preclinical studies. CABO and ABI have demonstrated an acceptable safety profile in metastatic castration resistant prostate cancer (mCRPC) (Choudhury et al Prostate 2018), and CABO and atezolizumab (ATEZO) in combination have showed a promising efficacy signal and manageable safety profile in mCRPC (COSMIC-021, NCT03170960; Agarwal ESMO 2021). The phase 3 CONTACT-02 trial (NCT04446117) is randomizing mCRPC pts to either CABO and ATEZO or a second generation ARTA. Given the robust preclinical and emerging clinical data for the use of both CABO and CPI therapy in advanced prostate cancer and the need to optimize therapy earlier in the course of disease, in the present trial we intend to evaluate the safety and tolerability of ABI, CABO, and CPI in mHSPC. Methods: CABIOS (NCT04477512) is a phase Ib, single center, open label trial of ABI, CABO and the CPI nivolumab (NIVO), an anti-PD-1 monoclonal antibody, in pts with mHSPC. Key inclusion criteria include histologically or cytologically confirmed metastatic prostate adenocarcinoma without neuroendocrine/small cell differentiation and radiographic evidence of metastatic disease. Ongoing androgen deprivation (ADT) within 12 weeks of study start is allowed. Key exclusion criteria include evidence of castration resistance, prior treatment with second-generation androgen receptor inhibitors, CYP17 inhibitors, CABO, or checkpoint inhibitor immunotherapy (anti-PD-1/PD-L1, CTLA-4), active autoimmune disease, and ongoing treatment with systemic corticosteroids daily. The primary objective of the trial is evaluation of the safety and tolerability of this combination therapy in the trial population; the primary endpoint is the frequency of dose-limiting toxicities (DLTs) as measured by CTCAE v5.0. The study will employ a 3 + 3 design evaluating ABI 1,000 mg once daily with prednisone 5 mg daily, NIVO 480 mg IV every 4 weeks, and a CABO starting dose of 20 mg once daily at dose level 1 (DL1). If 0 of 3 pts at DL1 experience a DLT, 3 pts will be enrolled at DL2 with CABO 40 mg once daily. If 1 of 3 pts at DL1 experience a DLT, 3 additional pts will be enrolled at DL1. If 0 of 3 pts experience a DLT at DL2, the study will move to a recommended phase 2 dose (RP2D) expansion cohort. Total sample size of approximately 20 pts is expected depending on DLT frequencies. Enrollment is ongoing. Clinical trial information: NCT04477512.

Phase 1 study of P-PSMA-101 CAR-T cells in patients with metastatic castration-resistant prostate cancer (mCRPC).

98 Background: P-PSMA-101 is an autologous CAR-T therapy targeting PSMA, with a high percentage of stem cell memory T cells (TSCM) associated with efficacy, safety, and bone homing (particularly relevant to prostate cancer). It is manufactured using a novel non-viral transposon system (piggyBac) that creates high TSCM products. Genes are inserted encoding a PSMA-targeted Centyrin CAR, iCasp9-based safety switch, and DHFR to purify CAR-T cells. P-PSMA-101 completely eliminated tumors in intractable murine models of prostate cancer, providing rationale for this phase 1 trial (NCT04249947). Methods: Patients with mCRPC treated with or not eligible for a CYP17 inhibitor or second-generation antiandrogen, and a taxane were enrolled. P-PSMA-101 was manufactured from apheresed T cells and administered IV following a standard 3-day cy/flu lymphodepletion regimen. Dose escalation from 0.25-15 x 106 cells/kg is planned. Results: As of September 30, 2021, P-PSMA-101 had been administered to 10 heavily pretreated patients (median 7 prior regimens; range 3-15). Single infusions of 0.25 (n=5) to 0.75 (n=5) x 106 cells/kg have been assessed, with dose escalation continuing. P-PSMA-101 cells were shown to expand in blood via qPCR assay, peaking 2-3 weeks after infusion, consistent with the high percentage of TSCM. Significant antitumor responses were seen in this preliminary data set. Declines in PSA were seen in 7 patients (&gt;50% in 3 and &gt;99% in 1). Of 4 patients who had pre- and post-treatment FDG and PSMA-PET imaging, 3 demonstrated marked to complete resolution of abnormal uptake at known metastatic disease sites, with concordance in bone and CT scans, and/or circulating tumor cells (CTC). In 1 case, post-treatment tumor biopsy demonstrated infiltration by P-PSMA-101 CAR-T cells and elimination of tumor cells (pathologic complete response). Safety was consistent with expectations for a CAR-T product. CRS was seen in 60% (10% Gr ≥3) of patients. DLT was seen in 1 patient with macrophage activation syndrome/uveitis, and was the only Gr ≥3 CRS event. Immune effector cell-associated neurotoxicity syndrome (ICANS) has not occurred. CRS marker elevations were modest (max IL-6: 642.6 pg/mL). The most common AEs were cytopenias, infections, and constitutional symptoms (Gr ≥3 60%, 10%, and 0%), as expected with lymphodepletion. Treatable related ocular AEs were noted in 3 patients. Conclusions: These results parallel preclinical findings that P-PSMA-101 can produce marked efficacy in mCRPC, and very low doses are highly efficacious, consistent with unique product attributes such as the TSCM phenotype and bone tropism. This is the first report demonstrating profound antitumor effects of a novel PSMA-directed CAR-T-cell platform with concordant biochemical, radiographic, and pathologic parameters, demonstrating that therapeutic benefit of unarmored CAR-T cells in a major solid tumor is possible. Clinical trial information: NCT04249947.

3D Microtissues Mimic the Architecture, Estradiol Synthesis, and Gap Junction Intercellular Communication of the Avascular Granulosa.

Humans are consistently exposed to thousands of untested chemicals that have been detected in the follicular fluid of the ovaries, and can disrupt reproductive health. Human granulosa cells (GCs) are the functional unit of the ovarian follicle with steroidogenic and signaling activities, and play a pivotal role in oocyte development. During follicle progression, GCs multiply to form a 3D avascular structure, and establish gap junction intercellular communication (GJIC) that is critical to maintaining optimal viability and function. We developed a high-throughput in vitro platform of human GCs for the screening of chemicals that can impact GJIC and estradiol (E2) production of human granulosa. Our granulosa 3D microtissues fabricated with human ovarian granulosa-like tumor KGN cells are multicell-layered structures that mimic the avascular granulosa layers surrounding the oocyte. These microtissues robustly expressed the steroidogenic CYP19 aromatase enzyme and GJIC intercellular membrane channel, connexin 43. Granulosa microtissues produced E2 at rates comparable to primary human GCs as previously reported. E2 production was suppressed by the CYP19 inhibitor, letrozole, and induced by CYP19 activators, bisphenol A at 100 µM, and genistein at 100 µM. Granulosa microtissues displayed active GJIC function, as demonstrated by the connexin 43-dependent diffusion of calcein fluorescent dye from microtissue surface to the core using high-throughput confocal microscopy in conjunction with our open-sourced automated image analysis tool. Overall, our 3D human granulosa screening platform is highly promising for predictive and efficient in vitro toxicity testing to screen for chemicals that contaminate follicular fluid and may affect fertility.

597P A phase I dose-escalation study of LAE001 in patients with metastatic castration-resistant prostate cancer (mCRPC)

Abiraterone, a CYP17 enzyme inhibitor, blocks the synthesis of androgens but causes the hyperaldosteronism that requires long term steroid use. The long term steroid use may cause serious side effects. LAE001 is a novel dual inhibitor of CYP17 and CYP11B2 (aldosterone synthase) that blocks both androgen and aldosterone synthesis. This study provided clinical evidences that LAE001 monotherapy is a safe medicine that can achieve androgen inhibition without hyperaldosteronism in patients with mCRPC.

Androgen receptor signaling inhibitors: post-chemotherapy, pre-chemotherapy and now in castration-sensitive prostate cancer.

Based on pioneering work by Huggins, Hodges and others, hormonal therapies have been established as an effective approach for advanced prostate cancer (PC) for the past eight decades. However, it quickly became evident that androgen deprivation therapy (ADT) via surgical or medical castration accomplishes inadequate inhibition of the androgen receptor (AR) axis, with clinical resistance inevitably emerging due to adrenal and intratumoral sources of androgens and other mechanisms. Early efforts to augment ADT by adding adrenal-targeting agents (aminoglutethimide, ketoconazole) or AR antagonists (flutamide, bicalutamide, nilutamide, cyproterone) failed to achieve overall survival (OS) benefits, although they did exhibit some evidence of limited clinical activity. More recently, four new androgen receptor signaling inhibitors (ARSIs) successfully entered clinical practice. Specifically, the CYP17 inhibitor abiraterone acetate and the second generation AR antagonists (enzalutamide, apalutamide and darolutamide) achieved OS benefits for PC patients, confirmed the importance of reactivated AR signaling in castration-resistant PC and validated important concepts that had been proposed in the field several decades ago but had remained so far unproven, including adrenal-targeted therapy and combined androgen blockade. The past decade has seen steady advances toward more comprehensive AR axis targeting. Now the question is raised whether we have accomplished the maximum AR axis inhibition possible or there is still room for improvement. This review, marking the 80-year anniversary of ADT and 10-year anniversary of successful ARSIs, examines their current clinical use and discusses future directions, in particular combination regimens, to maximize their efficacy, delay emergence of resistance and improve patient outcomes.

Cortisol as biomarker for CYP17 inhibition in mCRPC patients treated with abiraterone acetate.

5035 Background: Abiraterone acetate is an effective metastatic castration resistant prostate cancer (mCRPC) treatment, however, there is a high variability in response. It inhibits CYP17, thereby preventing the production of androgens. Abiraterone trough concentrations (Cmin) &gt; 8.4 ng/mL have been associated with an increased progression free survival (PFS) (Eur J Cancer. 2017;72:54-61; Prostate Cancer Prostatic Dis. 2020;23(2):244-251). However, plasma levels do not directly provide information on the level of CYP17 inhibition. Ideally, testosterone levels should be measured, but these levels are below the detection limit of available assays. The synthesis of cortisol is also inhibited by abiraterone via CYP17 inhibition and might therefore be a biomarker for CYP17 inhibition. The objective of this study was to investigate if cortisol levels are related to abiraterone levels and to clinical response. Methods: An observational study was performed in mCRPC patients treated with abiraterone acetate. At the outpatient clinic, plasma samples were collected for pharmacokinetic (PK) monitoring at each hospital visit. Reference populations of healthy volunteers and mCRPC patients using enzalutamide were included to investigate the influence of mCRPC and abiraterone treatment on the circadian rhythm of cortisol. Abiraterone and cortisol levels were measured using validated liquid chromatography-mass spectrometry (LC-MS/MS) assays. Clinical (prostate specific antigen (PSA) independent) PFS and PSA response were evaluated. Results: In total, 117 mCRPC patients using abiraterone acetate, 100 mCRPC patients using enzalutamide and 12 healthy volunteers were included. A clear circadian rhythm of cortisol was described in healthy volunteers and unaffected in mCRPC patients using enzalutamide. Contrarily, a circadian rhythm of cortisol could not be identified in mCRPC patients using abiraterone acetate, due to continuous suppression throughout the day. Patients with an abiraterone Cmin &gt; 8.4 ng/mL (n = 77) had a median cortisol concentration of 1.03 ng/mL vs. 2.59 ng/mL in patients with an abiraterone Cmin ≤8.4 ng/mL (n = 40) (p = 0.020). The median cortisol concentration in PSA responders (n = 63) was 1.02 ng/mL vs. 2.59 ng/mL for PSA non responders (n = 54) (p = 0.037). Patients in the highest cortisol tertile ( &gt; 3.03 ng/mL) had a median PFS of 3.7 months (n = 39) vs. 13.8 months in patients with cortisol levels ≤3.03 ng/mL (n = 78) (p = 0.007). The median PFS was 16.3 months in patients with an abiraterone Cmin &gt; 8.4 ng/mL and cortisol concentration &lt; 3.03 ng/ml vs. 5.3 months in patients with an abiraterone Cmin &gt; 8.4 ng/mL and cortisol concentration &gt; 3.03 ng/ml (p = 0.02). Conclusions: This study demonstrates that cortisol levels are of additional value to abiraterone concentrations as a marker for abiraterone acetate efficacy. This might help be helpful to assess efficacy of abiraterone treatment.

A phase 1/2a, open-label, multicenter study of intramuscular (IM) abiraterone decanoate (PRL-02) depot in patients with advanced prostate cancer (NCT04729114).

TPS5090 Background: PRL-02 is a long-acting IM formulation of a lipophilic abiraterone prodrug being developed for the treatment of patients with metastatic castration-sensitive (mCSPC) and metastatic castration-resistant prostate cancer (mCRPC). In nonclinical models, PRL-02 has a longer effective half-life and duration of action compared to oral abiraterone acetate (AA), due to slow release of the prodrug into circulation. PRL-02 is expected to provide greater abiraterone bioavailability and less variability in pharmacokinetics than oral AA. Based upon results in non-human primate models, PRL-02 should provide efficacy (e.g., testosterone [T] suppression) comparable to oral AA, but with lower abiraterone peak plasma concentrations and overall exposures, potentially leading to a superior therapeutic index and safety profile. The current trial is a phase 1/2a, open-label, dose escalation and subsequent dose expansion study of PRL-02 in men with metastatic prostate cancer. Study Objectives: The primary objective of this study is to determine a recommended phase 2 dose (RP2D) of PRL-02 that provides adequate T suppression up to 84 days. The secondary objectives of this study include the evaluation of safety and tolerability, the pharmacokinetic profile following IM administration and the pharmacodynamic effects of PRL-02. Methods: The phase 1 portion (Dose Escalation) is a standard 3+3 design intended to identify a RP2D that adequately suppresses T up to 84 days. The phase 2a portion (Dose Expansion) will confirm the safety, tolerability and pharmacodynamic effects of the RP2D. Main inclusion criteria are orchiectomy or ongoing GnRH analogue therapy for at least 3 months and a screening T level &lt;50 ng/dL but &gt;2 ng/dL. Prior treatment with abiraterone (or any other CYP17 inhibitor) and current treatment with enzalutamide or any other AR blocking agents are excluded. Patients will undergo scheduled periodic assessments of T levels. Patients may remain on study unless their T is &gt;1 ng/dL on two sequential determinations starting on Day 28 through Day 77 of the first dosing cycle. In phase 1, three patients will initially be enrolled at each dose. The starting dose is 180 mg (i.e., 1.0 mL of PRL-02) and dose escalation will proceed with a modified Fibonacci sequence. If none of the patients in a cohort experience a dose-limiting toxicity (DLT), the dose will be escalated in the next cohort of 3 patients. A DLT is defined as a drug-related Grade 3 or higher toxicity on the Common Terminology Criteria for Adverse Events v5.0, or meets drug-induced liver injury criteria, occurring during the first 28 days following the first dose. In phase 2a, 12 mCSPC and 12 mCRPC patients will be enrolled to receive up to 4 cycles of PRL-02 at the RP2D. The results of this phase 1/2a study will be presented at a future ASCO conference. Clinical trial information: NCT04729114.