Novel Androgen Receptor Inhibitors in Non-Metastatic, Castration-Resistant Prostate Cancer: A Systematic Review and Network Meta-Analysis

A multidisciplinary approach to address unmet needs in the management of patients with non-metastatic castration-resistant prostate cancer

BACKGROUND

With the availability of second-generation androgen receptor inhibitors (SGARIs), the treatment landscape has changed dramatically for patients with nonmetastatic castration-resistant prostate cancer (nmCRPC). In clinical trials, the SGARIs (apalutamide, enzalutamide, darolutamide) increased metastasis-free survival (MFS), overall survival (OS), and patient quality of life compared to placebo. These drugs were subsequently integrated into nmCRPC clinical practice guidelines. With advances in radiographic imaging, disease assessment, and patient monitoring, nmCRPC strategies are evolving to address limitations related to tracking disease progression using prostate-specific antigen (PSA) kinetics.

METHODS

A panel of 10 multidisciplinary experts in prostate cancer conducted reviews and discussions of unmet needs in the management and monitoring of patients with nmCRPC in order to develop consensus recommendations.

RESULTS

Across the SGARI literature, patient MFS and OS are generally comparable for all treatments, but important distinctions exist regarding short- and long-term drug safety profiles and drug-drug interactions. With respect to disease monitoring, a substantial proportion of patients using SGARIs may experience disease progression without rising PSA levels, suggesting a need for enhanced radiographic imaging in addition to PSA monitoring. Recent data also indicate that novel prostate-specific membrane antigen positron emission tomography radiotracers provide enhanced accuracy for disease detection, as compared to conventional imaging.

CONCLUSIONS

Clinical decision-making in nmCRPC has become more complex, with new opportunities to apply precision medicine to patient care. Multidisciplinary teams can ensure that patients with nmCRPC receive optimal and individualized disease management.

New advances of the androgen receptor in prostate cancer: report from the 1st International Androgen Receptor Symposium

The androgen receptor (AR) is a crucial player in various aspects of male reproduction and has been associated with the development and progression of prostate cancer (PCa). Therefore, the protein is the linchpin of current PCa therapies. Despite great research efforts, the AR signaling pathway has still not been deciphered, and the emergence of resistance is still the biggest problem in PCa treatment. To discuss the latest developments in AR research, the "1st International Androgen Receptor Symposium" offered a forum for the exchange of clinical and scientific innovations around the role of the AR in prostate cancer (PCa) and to stimulate new collaborative interactions among leading scientists from basic, translational, and clinical research. The symposium included three sessions covering preclinical studies, prognostic and diagnostic biomarkers, and ongoing prostate cancer clinical trials. In addition, a panel discussion about the future direction of androgen deprivation therapy and anti-AR therapy in PCa was conducted. Therefore, the newest insights and developments in therapeutic strategies and biomarkers are discussed in this report.

Discovery of potent pyrrolo-pyrimidine and purine HDAC inhibitors for the treatment of advanced prostate cancer

The development of drugs for the treatment of advanced prostate cancer (PCA) remains a challenging task. In this study we have designed, synthesized and tested twenty-nine novel HDAC inhibitors based on three different zinc binding groups (trifluoromethyloxadiazole, hydroxamic acid, and 2-mercaptoacetamide). These warheads were conveniently tethered to variously substituted phenyl linkers and decorated with differently substituted pyrrolo-pyrimidine and purine cap groups. Remarkably, most of the compounds showed nanomolar inhibitory activity against HDAC6. To provide structural insights into the Structure-Activity Relationships (SAR) of the investigated compounds, docking of representative inhibitors and molecular dynamics of HDAC6-inhibitor complexes were performed. Compounds of the trifluoromethyloxadiazole and hydroxamic acid series exhibited promising anti-proliferative activities, HDAC6 targeting in PCA cells, and in vitro tumor selectivity. Representative compounds of the two series were tested for solubility, cell permeability and metabolic stability, demonstrating favorable in vitro drug-like properties. The more interesting compounds were subjected to migration assays, which revealed that compound 13 and, to a lesser extent, compound 15 inhibited the invasive behaviour of androgen-sensitive and -insensitive advanced prostate cancer cells. Compound 13 was profiled against all HDACs and found to inhibit all members of class II HDACs (except for HDAC10) and to be selective with respect to class I and class IV HDACs. Overall, compound 13 combines potent inhibitory activity and class II selectivity with favorable drug-like properties, an excellent anti-proliferative activity and marked anti-migration properties on PCA cells, making it an excellent lead candidate for further optimization.

Darolutamide for non-metastatic castration-resistant prostate cancer: Efficacy, safety, and clinical perspectives of use

Darolutamide, a second-generation androgen receptor inhibitor (SGARI), has been shown to increase metastasis-free survival and overall survival among men with non-metastatic castration-resistant prostate cancer (nmCRPC). Its unique chemical structure potentially provides efficacy and safety advantages over the SGARIs apalutamide and enzalutamide, which are also indicated for nmCRPC. Despite a lack of direct comparisons, the SGARIs appear to have similar efficacy, safety, and quality of life (QoL) results. Indirect evidence suggests that darolutamide is preferred for its good adverse event profile, an attribute valued by physicians, patients, and their caregivers for maintaining QoL. Darolutamide and others in its class are costly; access may be a challenge for many patients and may lead to modifications to guideline-recommended regimens.

Safety differences across androgen receptor inhibitors in nonmetastatic castration-resistant prostate cancer

Approval of apalutamide, enzalutamide and darolutamide has transformed the treatment landscape and guideline recommendations for patients with nonmetastatic castration-resistant prostate cancer but now raises the issue of decision-making regarding treatment selection. In this commentary, we discuss the efficacy and safety of these second-generation androgen receptor inhibitors and propose that for patients with nonmetastatic castration-resistant prostate cancer, safety considerations for these treatments are especially important. We examine these considerations in the context of patient and caregiver preferences as well as patient clinical characteristics. We further posit that consideration of treatments' safety profiles should include not only the initial direct impacts from potential treatment-emergent adverse events and drug-drug interaction events, but also the full cascade of potentially avoidable healthcare complications.

Discovery of 2-(1-(3-Chloro-4-cyanophenyl)-1H-pyrazol-3-yl)acetamides as Potent, Selective, and Orally Available Antagonists Targeting the Androgen Receptor

The androgen receptor (AR) antagonists are efficient therapeutics for the treatment of prostate cancer (PCa). All the approved AR antagonists to date are targeted to the ligand-binding pocket (LBP) of AR and have suffered from various drug resistances, whereas AR antagonist targeting non-LBP site of AR is conceived as a promising strategy. Through the scaffold hopping of AR LBP antagonists, the 2-chloro-4-(1H-pyrazol-1-yl)benzonitrile was designed as a new core structure for AR antagonists. A total of 46 compounds were synthesized and biologically evaluated to disclose compounds 2f, 2k, and 4c, exhibiting potent AR antagonistic activities (IC₅₀ up to 69 nM), force against antiandrogen resistance, and untraditional targeting site of probably AR binding function 3. Therein, 4c exhibited effective tumor growth inhibition in LNCaP xenograft study upon oral administration. This work provides a novel chemical scaffold for AR antagonists and offers new perspective for the development of PCa therapy.

Sequential therapy with darolutamide in patients with non-metastatic castration-resistant prostate cancer resistant to enzalutamide or apalutamide

Enzalutamide, apalutamide, and darolutamide are currently recommended for patients with non-metastatic castration-resistant prostate cancer (nmCRPC), but cross-resistance of androgen receptor-axis-targeted therapies (ARAT) occurs. Because darolutamide has a distinct chemical structure to other non-steroidal antiandrogens, it may be effective for nmCRPC patients resistant to enzalutamide or apalutamide. We retrospectively evaluated the efficacy of switching to darolutamide in patients with nmCRPC. We included nine nmCRPC patients who experienced biochemical progression on enzalutamide or apalutamide and were switched over to darolutamide. Five patients (55.5%) had a PSA response >50% decline after starting darolutamide, with an average of 73% PSA decline. Median progression-free survival was 6 months. In conclusion, an ARAT switch from enzalutamide or apalutamide to darolutamide might be effective for nmCRPC. Although the validation in a large-scale cohort is necessary, the switch to darolutamide could be a promising therapeutic option after the progression of 1st line ARAT in nmCRPC patients.

Decisions and dilemmas in non-metastatic castration-resistant prostate cancer management

Non-metastatic castration-resistant prostate cancer (nmCRPC) indicates a condition characterized by the progression of the prostate-specific antigen without radiographic evidence of distant metastasis on conventional imaging during androgen deprivation therapy (ADT). Recently, 3 phase III trials have shown that the addition of next-generation androgen-receptor inhibitors (ARIs) apalutamide, darolutamide, and enzalutamide to ADT allows patients with high-risk nmCRPC to delay the appearance of metastasis and to obtain long-term clinical benefits. However, the lack of head-to head comparison makes it difficult to choose one among these agents. We reviewed the literature and explained the rationale of the possible therapeutic choices. In any case, the availability of novel ARIs means that patients with nmCRPC have now a new effective treatment option that provides them a renewed hope.

The Use of High-Intensity Focused Ultrasound (HIFU) Plus 150mg Bicalutamide as First Line Salvage Therapy for Local Recurrent Prostate Cancer

Patients with localized prostate cancer (PCa) are often treated with radical prostatectomy (RP). However, more than 30% of such patients have high risk of recurrence. Salvage radiotherapy (SRT), androgen deprivation therapy (ADT) and combination of radiotherapy and ADT are the standard care for recurrent PCa. Recently, high intensity focused ultrasound (HIFU) has gradually applied in the treatment of recurrent PCa. Here, we proposed a hypothesis that combined HIFU and bicalutamide 150mg as first line salvage therapy to treat patients with local recurrent PCa with visible lesions due to the following advantages: (1) HIFU is effective in reducing local tumor load, and bicalutamide 150mg is a feasible and safety option to combine with HIFU. (2) Compared with radiotherapy, HIFU plus 150mg bicalutamide is minimal invasiveness with fewer adverse effects and better quality of life(QOL); (3) Radiotherapy can be preserved as the second-line salvage method in the cases who are failure to HIFU and 150mg bicalutamide combination. More clinical trials are warranted to confirm this hypothesis in treatment with recurrent PCa.