Androgen receptor signalling impairs docetaxel efficacy in castration-resistant prostate cancer

Drug resistance in human cancers - Mechanisms and implications

Cancers have complex etiology and pose a significant impact from the health care perspective apart from the socio-economic implications. The enormity of challenge posed by cancers can be understood from the fact that clinical trials for cancer therapy has yielded minimum potential promises compared to those obtained for other diseases. Surgery, chemotherapy and radiotherapy continue to be the mainstay therapeutic options for cancers. Among the challenges posed by these options, induced resistance to chemotherapeutic drugs is probably the most significant contributor for poor prognosis and ineffectiveness of the therapy. Drug resistance is a property exhibited by almost all cancer types including carcinomas, leukemias, myelomas, sarcomas and lymphomas. The mechanisms by which drug resistance is induced include the factors within the tumor microenvironment, mutations in the genes responsible for drug metabolism, changes in the surface drug receptors and increased drug efflux. We present here comprehensively the drug resistance in cancers along with their mechanisms. Also, apart from resistance to regularly used chemotherapeutic drugs, we present resistance induction to new generation therapeutic agents such as monoclonal antibodies. Finally, we have discussed the experimental approaches to understand the mechanisms underlying induction of drug resistance and potential ways to mitigate induced drug resistance.

ATPase Copper Transporting Beta (ATP7B) Is a Novel Target for Improving the Therapeutic Efficacy of Docetaxel by Disulfiram/Copper in Human Prostate Cancer

Docetaxel has been the standard first-line chemotherapy for lethal metastatic prostate cancer (mPCa) since 2004, but resistance to docetaxel treatment is common. The molecular mechanisms of docetaxel resistance remain largely unknown and could be amenable to interventions that mitigate resistance. We have recently discovered that several docetaxel-resistant mPCa cell lines exhibit lower uptake of cellular copper and uniquely express higher levels of a copper exporter protein ATP7B. Knockdown of ATP7B by silencing RNAs (siRNA) sensitized docetaxel-resistant mPCa cells to the growth-inhibitory and apoptotic effects of docetaxel. Importantly, deletions of ATP7B in human mPCa tissues predict significantly better survival of patients after their first chemotherapy than those with wild-type ATP7B (P = 0.0006). In addition, disulfiram (DSF), an FDA-approved drug for the treatment of alcohol dependence, in combination with copper, significantly enhanced the in vivo antitumor effects of docetaxel in a docetaxel-resistant xenograft tumor model. Our analyses also revealed that DSF and copper engaged with ATP7B to decrease protein levels of COMM domain-containing protein 1 (COMMD1), S-phase kinase-associated protein 2 (Skp2), and clusterin and markedly increase protein expression of cyclin-dependent kinase inhibitor 1 (p21/WAF1). Taken together, our results indicate a copper-dependent nutrient vulnerability through ATP7B exporter in docetaxel-resistant prostate cancer for improving the therapeutic efficacy of docetaxel.

Darolutamide Added to Docetaxel Augments Antitumor Effect in Models of Prostate Cancer through Cell Cycle Arrest at the G1-S Transition

Resistance to taxane chemotherapy is frequently observed in metastatic prostate cancer. The androgen receptor (AR) is a major driver of prostate cancer and a key regulator of the G1-S cell-cycle checkpoint, promoting cancer cell proliferation by irreversible passage to the S-phase. We hypothesized that AR signaling inhibitor (ARSi) darolutamide in combination with docetaxel could augment antitumor effect by impeding the proliferation of taxane-resistant cancer cells. We monitored cell viability in organoids, tumor volume, and PSA secretion in patient-derived xenografts (PDX) and analyzed cell cycle and signaling pathway alterations. Combination treatment increased antitumor effect in androgen-sensitive, AR-positive prostate cancer organoids and PDXs. Equally beneficial effects of darolutamide added to docetaxel were observed in a castration-resistant model, progressive on docetaxel, enzalutamide, and cabazitaxel. In vitro studies showed that docetaxel treatment with simultaneous darolutamide resulted in a reduction of cells entering the S-phase in contrast to only docetaxel. Molecular analysis in the prostate cancer cell line LNCaP revealed an upregulation of cyclin-dependent kinase inhibitor p21, supporting blockade of S-phase entry and cell proliferation. Our results provide a preclinical support for combining taxanes and darolutamide as a multimodal treatment strategy in patients with metastatic prostate cancer progressive on ARSi and taxane chemotherapy.

Interplay of Ritonavir-Boosted Oral Cabazitaxel with the Organic Anion-Transporting Polypeptide (OATP) Uptake Transporters and Carboxylesterase 1 in Mice

Intravenously administered chemotherapeutic cabazitaxel is used for palliative treatment of prostate cancer. An oral formulation would be more patient-friendly and reduce the need for hospitalization. We therefore study determinants of the oral pharmacokinetics of cabazitaxel in a ritonavir-boosted setting, which reduces the CYP3A-mediated first-pass metabolism of cabazitaxel. We here assessed the role of organic anion-transporting polypeptides (OATPs) in the disposition of orally boosted cabazitaxel and its active metabolites, using the Oatp1a/b-knockout and the OATP1B1/1B3-transgenic mice. These transporters may substantially affect plasma clearance and hepatic and intestinal drug disposition. The pharmacokinetics of cabazitaxel and DM2 were not significantly affected by Oatp1a/b and OATP1B1/1B3 activity. In contrast, the plasma AUC0-120 min of DM1 in Oatp1a/b-/- was 1.9-fold (p < 0.05) higher than that in wild-type mice, and that of docetaxel was 2.4-fold (p < 0.05) higher. We further observed impaired hepatic uptake and intestinal disposition for DM1 and docetaxel in the Oatp-ablated strains. None of these parameters showed rescue by the OATP1B1 or -1B3 transporters in the humanized mouse strains, suggesting a minimal role of OATP1B1/1B3. Ritonavir itself was also a potent substrate for mOatp1a/b, showing a 2.9-fold (p < 0.0001) increased plasma AUC0-120 min and 3.5-fold (p < 0.0001) decreased liver-to-plasma ratio in Oatp1a/b-/- compared to those in wild-type mice. Furthermore, we observed the tight binding of cabazitaxel and its active metabolites, including docetaxel, to plasma carboxylesterase (Ces1c) in mice, which may complicate the interpretation of pharmacokinetic and pharmacodynamic mouse studies. Collectively, these results will help to further optimize (pre)clinical research into the safety and efficacy of orally applied cabazitaxel.

Gαi2 Protein Inhibition Blocks Chemotherapy- and Anti-Androgen-Induced Prostate Cancer Cell Migration

We have previously shown that heterotrimeric G-protein subunit alphai2 (Gαi2) is essential for cell migration and invasion in prostate, ovarian and breast cancer cells, and novel small molecule inhibitors targeting Gαi2 block its effects on migratory and invasive behavior. In this study, we have identified potent, metabolically stable, second generation Gαi2 inhibitors which inhibit cell migration in prostate cancer cells. Recent studies have shown that chemotherapy can induce the cancer cells to migrate to distant sites to form metastases. In the present study, we determined the effects of taxanes (docetaxel), anti-androgens (enzalutamide and bicalutamide) and histone deacetylase (HDAC) inhibitors (SAHA and SBI-I-19) on cell migration in prostate cancer cells. All treatments induced cell migration, and simultaneous treatments with new Gαi2 inhibitors blocked their effects on cell migration. We concluded that a combination treatment of Gαi2 inhibitors and chemotherapy could blunt the capability of cancer cells to migrate and form metastases.

Understanding the role of Pax5 in development of taxane-resistant neuroendocrine like prostate cancers

Resistance to the current Androgen Receptor Signaling Inhibitor (ARSI) therapies has led to higher incidences of therapy-induced neuroendocrine-like prostate cancer (t-NEPC). This highly aggressive subtype with predominant small cell-like characteristics is resistant to taxane chemotherapies and has a dismal overall survival. t-NEPCs are mostly treated with platinum-based drugs with a combination of etoposide or taxane and have less selectivity and high systemic toxicity, which often limit their clinical potential. During t-NEPC transformation, adenocarcinomas lose their luminal features and adopt neuro-basal characteristics. Whether the adaptive neuronal characteristics of t-NEPC are responsible for such taxane resistance remains unknown. Pathway analysis from patient gene-expression databases indicates that t-NEPC upregulates various neuronal pathways associated with enhanced cellular networks. To identify transcription factor(s) (TF) that could be important for promoting the gene expression for neuronal characters in t-NEPC, we performed ATAC-Seq, acetylated-histone ChIP-seq, and RNA-seq in our NE-like cell line models and analyzed the promoters of transcriptionally active and significantly enriched neuroendocrine-like (NE-like) cancer-specific genes. Our results indicate that Pax5 could be an important transcription factor for neuronal gene expression and specific to t-NEPC. Pathway analysis revealed that Pax5 expression is involved in axonal guidance, neurotransmitter regulation, and neuronal adhesion, which are critical for strong cellular communications. Further results suggest that depletion of Pax5 disrupts cellular interaction in NE-like cells and reduces surface growth factor receptor activation, thereby, sensitizing them to taxane therapies. Moreover, t-NEPC specific hydroxymethylation of Pax5 promoter CpG islands favors Pbx1 binding to induce Pax5 expression. Based on our study, we concluded that continuous exposure to ARSI therapies leads to epigenetic modifications and Pax5 activation in t-NEPC, which promotes the expression of genes necessary to adopt taxane-resistant NE-like cancer. Thus, targeting the Pax5 axis can be beneficial for reverting their taxane sensitivity.

Icariin-Curcumol promotes docetaxel sensitivity in prostate cancer through modulation of the PI3K-Akt signaling pathway and the Warburg effect

BACKGROUND

Docetaxel (DTX) resistance reduces therapeutic efficacy in prostate cancer (PCa). Accumulating reports support the role of phytochemicals in the reversal of DTX resistance. This study aimed to determine whether Epimedium brevicornu and Curcuma zedoaria extracts (ECe), specially icariin-curcumol, attenuates DTX resistance and explore their potential mechanisms.

METHODS

Regulatory pathways were predicted between ECe active ingredients and PCa using network pharmacology. DTX-resistant cell LNCaP/R were established based on DTX-sensitive LNCaP, and xenograft models were further established. Active ingredients in ECe by HLPC-MS were identified. The binding of icariin and curcumol to the target was analyzed by molecular docking. Biochemical experiments were applied to determine the possible mechanisms by which Icariin-Curcumol regulates DTX sensitivity.

RESULTS

Akt1 and the PI3K-Akt signaling pathway were predicted as the primary functional target between drug and PCa. ECe and DTX inhibited xenograft tumor growth, inflammation, cell viability and promoted apoptosis. Icariin and curcumol were detected in ECe, and icariin and curcumol docked with Akt1. ECe, Icariin-Curcumol and DTX downregulated AR, PSA, PI3K, Akt1, mTOR, and HIF-1ɑ. Moreover, ECe, Icariin-Curcumol and DTX increased glucose and PDH, decreased lactic acid, ATP and LDH, and downregulated c-Myc, hnRNPs, VEGF, PFK1, and PKM2. Notably, the anti-PCa effect of DTX was attenuated compared to ECe or Icariin-Curcumol in the LNCaP/R model. The combined effect of Icariin-Curcumol and DTX was superior to that of DTX.

CONCLUSION

Our data support that Icariin-Curcumol reverses DTX resistance by inhibiting the PI3K-Akt signaling and the Warburg effect, providing new ideas for improving therapeutic measures for PCa.

Cuproptosis enhances docetaxel chemosensitivity by inhibiting autophagy via the DLAT/mTOR pathway in prostate cancer

Cuproptosis, a newly discovered programmed cell death induced by copper ions, is associated with the progression and drug resistance of various tumors. Docetaxel plays a vital role as a first-line chemotherapeutic agent for advanced prostate cancer; however, most patients end up with prostate cancer progression because of inherent or acquired resistance. Herein, we examined the role of cuproptosis in the chemotherapeutic resistance of prostate cancer to docetaxel. We treated prostate cancer cell lines with elesclomol-CuCl2 , as well as with docetaxel. We performed analyses of CCK8, colony formation tests, cell cycle flow assay, transmission electron microscopy, and mTOR signaling in treated cells, and treated a xenograft prostate cancer model with elesclomol-CuCl2 and docetaxel in vivo, and performed immunohistochemistry and Western blotting analysis in treated tumors. We found that elesclomol-CuCl2 could promote cell death and enhance chemosensitivity to docetaxel. Elesclomol-CuCl2 induced cell death and inhibited the growth of prostate cancer cells relying on copper ions-induced cuproptosis, not elesclomol. In addition, dihydrolipoamide S-acetyltransferase (DLAT) was involved in cuproptosis-enhanced drug sensitivity to docetaxel. Mechanistically, upregulated DLAT by cuproptosis inhibited autophagy, promoted G2/M phase retention of cells, and enhanced the sensitivity to docetaxel chemotherapy in vitro and in vivo via the mTOR signaling pathway. Our findings demonstrated that the cuproptosis-regulated DLAT/mTOR pathway inhibited autophagy and promoted cells in G2/M phase retention, thus enhancing the chemosensitivity to docetaxel. This discovery may provide an effective therapeutic option for treating advanced prostate cancer by inhibiting the chemotherapeutic resistance to docetaxel.

Androgen receptor knockdown enhances prostate cancer chemosensitivity by down-regulating FEN1 through the ERK/ELK1 signalling pathway

PURPOSE

Flap endonuclease 1 (FEN1) is highly upregulated in prostate cancer and promotes the growth of prostate cancer cells. Androgen receptor (AR) is the most critical determinant of the occurrence, progression, metastasis, and treatment of prostate cancer. However, the effect of FEN1 on docetaxel (DTX) sensitivity and the regulatory mechanisms of AR on FEN1 expression in prostate cancer need to be further studied.

METHODS

Bioinformatics analyses were performed using data from the Cancer Genome Atlas and the Gene Expression Omnibus. Prostate cancer cell lines 22Rv1 and LNCaP were used. FEN1 siRNA, FEN1 overexpression plasmid, and AR siRNA were transfected into cells. Biomarker expression was evaluated by immunohistochemistry and Western blotting. Apoptosis and the cell cycle were explored using flow cytometry analysis. Luciferase reporter assay was performed to verify the target relationship. Xenograft assays were conducted using 22Rv1 cells to evaluate the in vivo conclusions.

RESULTS

Overexpression of FEN1 inhibited cell apoptosis and cell cycle arrest in the S phase induced by DTX. AR knockdown enhanced DTX-induced cell apoptosis and cell cycle arrest at the S phase in prostate cancer cells, which was attenuated by FEN1 overexpression. In vivo experiments showed that overexpression of FEN1 significantly increased tumour growth and weakened the inhibitory effect of DTX on prostate tumour growth, while AR knockdown enhance the sensitivity of DTX to prostate tumour. AR knockdown resulted in FEN1, pho-ERK1/2, and pho-ELK1 downregulation, and the luciferase reporter assay confirmed that ELK1 can regulate the transcription of FEN1.

CONCLUSION

Collectively, our studies demonstrate that AR knockdown improves the DTX sensitivity of prostate cancer cells by downregulating FEN1 through the ERK/ELK1 signalling pathway.

Predictive factors associated with differential pathologic response to neoadjuvant chemohormonal therapy in high-risk localized prostate cancer

PURPOSE

To explore the clinical parameters and molecular biomarkers that can predict differential pathologic response to neoadjuvant chemohormonal therapy (NCHT) in prostate cancer (CaP).

METHODS

A total of 128 patients with primary high-risk localized CaP who had received NCHT followed by radical prostatectomy (RP) were included. Androgen receptor (AR), AR splice variant-7 (AR-V7) and Ki-67 staining were evaluated in prostate biopsy specimens by immunohistochemistry. The pathologic response to NCHT in whole mount RP specimens was measured based on the reduction degree of tumor volume and cellularity compared to the paired pretreatment needle biopsy, and divided into 5 tier grades (Grades 0-4). Patients with Grades 2 to 4 (the reduction degree more than 30%) were defined as having a favorable response. Logistic regression was performed to explore the predictive factors associated with a favorable pathologic response. The predictive accuracy was evaluated by receiver operating characteristic (ROC) curve and area under the ROC curve (AUC).

RESULTS

Ninety-seven patients (75.78%) had a favorable response to NCHT. Logistic regression showed that the preoperative PSA level, low AR expression and high Ki-67 expression in biopsy specimens were associated with a favorable pathologic response (P < 0.05). Furthermore, the AUC of the preoperative PSA level, AR and Ki-67 were 0.625, 0.624 and 0.723, respectively. Subgroup analysis revealed that the rate of favorable pathologic response to NCHT was 88.5% in patients with AR^lowKi-67^high, which was higher than patients with AR^lowKi-67^low, AR^highKi-67^low, and AR^highKi-67^high (88.5% vs. 73.9%, 72.9%, and 70.9%, all P < 0.05).

CONCLUSIONS

A lower preoperative PSA level was an independent predictive factor for a favorable pathologic response. Moreover, the expression status of AR and Ki-67 in biopsy specimens were associated with differential pathologic response to NCHT, and AR low/Ki-67 high was also associated with favorable response but warrants further evaluation in this patient subgroup and future trial clinical trial design.

PDZRN4 suppresses tumorigenesis and androgen therapy-resistance in prostate cancer

Background: PDZRN4 (PDZ domain-containing RING finger 4), a member of the LNX (ligand of numb protein-X) family that regulates the levels of NUMB, plays a critical role in suppressing the proliferation and invasion of hormone-related malignant tumours. There are few studies on the role of PDZRN4 in the pathogenesis of prostate cancer (PCa). We aimed to examine whether PDZRN4 regulates the growth and development of PCa.

Methods: Cell transduction and Western blotting were used to establish and confirm PDZRN4 knock down in PC cells. Using the MTT, wound healing, transwell migration, and animal experiments, we explored the biological function of PDZRN4 knockdown (PDZRN4-kd) cells. Via PCR and immunohistochemistry, the mRNA and protein expression of PDZRN4 was examined in PC cells and tissues.

Results: Hormone-dependent (LNCap) and hormone-independent (DU145, PC3, and C4-2) PC lines were transfected with lentivirus carrying PDZRN4 shRNA. The Western blotting results showed that the expression of PDZRN4 was stably downregulated in PDZRN4 knockdown (PDZRN4-kd) cells. The proliferation, invasion and migration of PDZRN4-kd cells were dramatically increased in vivo. To explore the expression of PDZRN4 in prostate cancer samples, we analysed TCGA data and found that PDZRN4 was negatively correlated with the development of PC. PDZRN4 levels were downregulated by androgen deprivation in hormone-sensitive cells. Moreover, PDZRN4 failed to induce proliferation in DU145 cells with androgen deprivation.

Conclusions: PDZRN4 is a functional suppressor of prostate cancer growth and development and is a potential target of biochemical therapy in hormone-resistant PC.

Development and Evaluation of a PSMA-Targeted Nanosystem Co-Packaging Docetaxel and Androgen Receptor siRNA for Castration-Resistant Prostate Cancer Treatment

Primary prostate cancer (PC) progresses to castration-resistant PC (CRPC) during androgen deprivation therapy (ADR) in early stages of prostate cancer. Thus, rather than blocking the androgen-related pathway further, docetaxel (DTX)-based therapy has become the most effective and standard first-line chemotherapy for CRPC. Although the therapy is successful in prolonging the survival of patients with CRPC, chemotherapy resistance develops due to the abnormal activation of the androgen receptor (AR) signaling pathway. Thus, to optimize DTX efficacy, continued maximum suppression of androgen levels and AR signaling is required. Here, we designed a prostate-specific membrane antigen (PSMA)-targeted nanosystem to carry both DTX and AR siRNA (Di-PP/AR-siRNA/DTX) for CRPC treatment. Specifically, DTX was encapsulated into the hydrophobic inner layer, and the AR siRNA was then condensed with the cationic PEI block in the hydrophilic outer layer of the PEI-PLGA polymeric micelles. The micelles were further coated with PSMA-targeted anionic polyethylene glycol-polyaspartic acid (Di-PEG-PLD). In vitro and in vivo results demonstrated that the resulting Di-PP/AR-siRNA/DTX exhibited prolonged blood circulation, selective targeting, and enhanced antitumor effects. Consequently, Di-PP/AR-siRNA/DTX holds great potential for efficient CRPC treatment by combining chemotherapy and siRNA silencing of androgen-related signaling pathways.

Transforming growth factor-beta (TGF-β) in prostate cancer: A dual function mediator?

Transforming growth factor-beta (TGF-β) is a member of a family of secreted cytokines with vital biological functions in cells. The abnormal expression of TGF-β signaling is a common finding in pathological conditions, particularly cancer. Prostate cancer (PCa) is one of the leading causes of death among men. Several genetic and epigenetic alterations can result in PCa development, and govern its progression. The present review attempts to shed some light on the role of TGF-β signaling in PCa. TGF-β signaling can either stimulate or inhibit proliferation and viability of PCa cells, depending on the context. The metastasis of PCa cells is increased by TGF-β signaling via induction of EMT and MMPs. Furthermore, TGF-β signaling can induce drug resistance of PCa cells, and can lead to immune evasion via reducing the anti-tumor activity of cytotoxic T cells and stimulating regulatory T cells. Upstream mediators such as microRNAs and lncRNAs, can regulate TGF-β signaling in PCa. Furthermore, some pharmacological compounds such as thymoquinone and valproic acid can suppress TGF-β signaling for PCa therapy. TGF-β over-expression is associated with poor prognosis in PCa patients. Furthermore, TGF-β up-regulation before prostatectomy is associated with recurrence of PCa. Overall, current review discusses role of TGF-β signaling in proliferation, metastasis and therapy response of PCa cells and in order to improve knowledge towards its regulation, upstream mediators of TGF-β such as non-coding RNAs are described. Finally, TGF-β regulation and its clinical application are discussed.

Continued Androgen Signalling Inhibition improves Cabazitaxel Efficacy in Prostate Cancer

BACKGROUND

The androgen receptor (AR) pathway is a key driver of neoplastic behaviour in the different stages of metastatic prostate cancer (mPCa). Targeting the AR therefore remains the cornerstone for mPCa treatment. We have previously reported that activation of AR signalling affects taxane chemo-sensitivity in preclinical models of castration resistant PCa (CRPC). Here, we explored the anti-tumour efficacy of the AR targeted inhibitor enzalutamide combined with cabazitaxel.

METHODS

We used the AR positive CRPC model PC346C-DCC-K to assess the in vitro and in vivo activity of combining enzalutamide with cabazitaxel. Subsequent validation studies were performed using an enzalutamide resistant VCaP model. To investigate the impact of AR signalling on cabazitaxel activity we used quantitative live-cell imaging of tubulin stabilization and apoptosis related nuclear fragmentation.

FINDINGS

Enzalutamide strongly amplified cabazitaxel anti-tumour activity in the patient-derived xenograft models PC346C-DCC-K (median time to humane endpoint 77 versus 48 days, P<0.0001) and VCaP-Enza-B (median time to humane endpoint 80 versus 53 days, P<0.001). Although enzalutamide treatment by itself was ineffective in reducing tumour growth, it significantly suppressed AR signalling in PC346C-DCC-K tumours as shown by AR target gene expression. The addition of enzalutamide enhanced cabazitaxel induced apoptosis as shown by live-cell imaging (P<0.001).

INTERPRETATION

Our study demonstrates that cabazitaxel efficacy can be improved by simultaneous blocking of AR signalling by enzalutamide, even if AR targeted treatment no longer affects tumour growth. These findings support clinical studies that combine AR targeted inhibitors with cabazitaxel in CRPC.

Modeling Prostate Cancer Treatment Responses in the Organoid Era: 3D Environment Impacts Drug Testing

Organoid-based studies have revolutionized in vitro preclinical research and hold great promise for the cancer research field, including prostate cancer (PCa). However, experimental variability in organoid drug testing complicates reproducibility. For example, we observed PCa organoids to be less affected by cabazitaxel, abiraterone and enzalutamide as compared to corresponding single cells prior to organoid assembly. We hypothesized that three-dimensional (3D) organoid organization and the use of various 3D scaffolds impact treatment efficacy. Live-cell imaging of androgen-induced androgen receptor (AR) nuclear translocation and taxane-induced tubulin stabilization was used to investigate the impact of 3D scaffolds, spatial organoid distribution and organoid size on treatment effect. Scaffolds delayed AR translocation and tubulin stabilization, with Matrigel causing a more pronounced delay than synthetic hydrogel as well as incomplete tubulin stabilization. Drug effect was further attenuated the more centrally organoids were located in the scaffold dome. Moreover, cells in the organoid core revealed a delayed treatment effect compared to cells in the organoid periphery, underscoring the impact of organoid size. These findings indicate that analysis of organoid drug responses needs careful interpretation and requires dedicated read-outs with consideration of underlying technical aspects.

Cabazitaxel multiple rechallenges in metastatic castration-resistant prostate cancer

Introduction

Cabazitaxel multiple rechallenges may be a treatment option in heavily pretreated patients with metastatic castration‐resistant prostate cancer (mCRPC) who had a good initial response to cabazitaxel and who are still fit to receive it. Our objective was to assess the efficacy and toxicity of multiple rechallenges.

Patients and methods

We retrospectively identified 22 mCRPC patients previously treated with docetaxel and/or androgen receptor‐targeted agents who received multiple cabazitaxel rechallenges in 9 French centers. Cabazitaxel was initiated at a dose of 25 mg/m² q3week. A reduced dose (20 mg/m² q3w) or an alternative schedule (mainly 16 mg/m² q2w) was increasingly used for subsequent rechallenges. Progression‐free survival, prostate‐specific antigen (PSA) response, best clinical response, and grade ≥3 toxicities were collected. Overall survival was calculated from various time points.

Results

Twenty‐two patients with an initial response to cabazitaxel were rechallenged at least twice. The median number of cabazitaxel cycles was 7 at first cabazitaxel treatment, 6 at first rechallenge, and 5 at subsequent rechallenges. Median progression‐free survival at first rechallenge was 9.6 months and 5.6 months at second rechallenge. Median overall survival was 50.9 months from the first cabazitaxel dose, 114.9 months from first life‐extending therapy initiation in mCRPC, and 105 months from mCRPC diagnosis. There was no cumulative grade ≥3 neuropathy or nail disorder and one case of febrile neutropenia.

Conclusion

Cabazitaxel multiple rechallenges may be a treatment option without cumulative toxicity in heavily pretreated patients having a good response to first cabazitaxel use and still fit to receive it.

Novelty & Impact Statements

Patients with metastatic castration‐resistant prostate cancer can be treated with Cabazitaxel after docetaxel and androgen receptor‐targeted agent. This chemotherapy can be used multiple times with efficacy and manageable toxicity.

Pharmacokinetics of docetaxel and ritonavir after oral administration of ModraDoc006/r in patients with prostate cancer versus patients with other advanced solid tumours

PURPOSE

ModraDoc006 is a novel oral formulation of docetaxel. The clearance of intravenous docetaxel is higher in medically castrated prostate cancer patients as compared to patients with other types of solid tumours. Oral docetaxel requires co-administration ritonavir (r), which might further impact the pharmacokinetics (PK). We now compare the PK of docetaxel and ritonavir between patients with Hormone Sensitive Prostate Cancer (HSPC), metastatic Castration-Resistant Prostate Cancer (mCRPC) and other metastatic solid tumours, treated on the same dose and weekly schedule of ModraDoc006/r.

METHODS

The docetaxel and ritonavir PK were compared between four patient groups from three clinical phase I trials, including eight male and eight female patients with different types of solid tumours (study 1), seven patients with HSPC (study 2) and five patients with mCRPC (study 3). All patients were treated with ModraDoc006 30 mg and ritonavir 100 mg in the morning, followed by ModraDoc006 20 mg and ritonavir 100 mg in the evening (ModraDoc006/r 30-20/100-100). For comparative purposes, the PK of six mCRPC patients that received 30-20/200-100 in study 3 were also evaluated.

RESULTS

The maximum plasma concentration (C_max) was significantly lower for both docetaxel and ritonavir in the prostate cancer patients as compared to the patients with other types of solid tumours treated at ModraDoc006/r 30-20/100-100. The docetaxel area under the plasma concentration versus time curve (AUC) was significantly different at this dose, with a mean AUC_0-48 of 1359 ± 374 ng/mL*h (N = 8) in female patients and 894 ± 223 ng/mL*h (N = 8) in male patients with different solid tumours (study 1), 321 ± 81 (N = 7) in HSPC (study 2) and 367 ± 182 ng/mL*h (N = 5) in mCRPC (study 3). A similar pattern was observed for ritonavir. ModraDoc006/r 30-20/200-100 in six mCRPC patients led to a comparable ritonavir exposure as compared to the patients at 30-20/100-100 in study 1 and increased the docetaxel AUC_0-48 to 1266 ± 473 ng/mL*h (N = 6).

CONCLUSION

The exposure to docetaxel and ritonavir was significantly lower in prostate cancer patients as compared to patients with other types of solid tumours, treated on ModraDoc006/r 30-20/100-100. An increase of the ritonavir dose increased the docetaxel exposure in mCRPC patients. Therefore, a different RP2D of ModraDoc006/r is pursued in castrated prostate cancer patients as compared to patients with other types of solid tumours.

TRIAL REGISTRATION

Study 1: ClinicalTrials.gov Identifier NCT01173913, date of registration August 2, 2010. Study 2: ClinicalTrials.gov Identifier NCT03066154, date of registration February 28, 2017. Study 3: ClinicalTrials.gov Identifier NCT03136640, date of registration May 2, 2017.