sirolimus and bicalutamide

Recent data indicate that there is a significant cross-talk between the PI3K/Akt/mTOR and androgen receptor signaling pathways. We evaluated safety and tolerability as well as potential drug-drug interaction of ridaforolimus, a mammalian target of rapamycin (mTOR) inhibitor, when combined with the androgen receptor inhibitor bicalutamide in patients with asymptomatic, metastatic castration-resistant prostate cancer.. Patients were treated with the combination of ridaforolimus 30 mg/day for 5 consecutive days each week and bicalutamide 50 mg/day. Ridaforolimus pharmacokinetics was assessed with and without bicalutamide.. Twelve patients were enrolled including 1 screen failure. Dose reductions were required in 7 patients. Three of the 11 patients experienced a dose-limited toxicity, 1 with Grade 3 hyperglycemia and 2 with Grade 2 stomatitis leading to <75 % of planned ridaforolimus dose during the first 35 days of study treatment. The pharmacokinetic results showed no differences in exposures to ridaforolimus with and without concomitant bicalutamide administration.. Although there was no evidence of a clinically relevant pharmacological drug-drug interaction, the occurrence of dose-limiting toxicities in 3 of 11 evaluable patients at a reduced dose of ridaforolimus of 30 mg/day suggests that this combination may not be well suited for asymptomatic or minimally symptomatic prostate cancer patients.

Topics: Aged; Androgen Antagonists; Anilides; Antineoplastic Combined Chemotherapy Protocols; Dose-Response Relationship, Drug; Drug Interactions; Follow-Up Studies; Humans; Male; Maximum Tolerated Dose; Middle Aged; Neoplasm Metastasis; Nitriles; Orchiectomy; Prospective Studies; Prostatic Neoplasms; Sirolimus; TOR Serine-Threonine Kinases; Tosyl Compounds

Study Type--Therapy (cohort) Level of Evidence 2a. What's known on the subject? and What does the study add? Despite expanding treatment options for castration-resistant prostate cancer (CRPC), therapies with long response duration remain intangible due to prostate cancer cells' natural ability to develop iterative resistance. Androgen receptor (AR) signaling has been shown to play a critical role in CRPC and its expression is regulated by the PI3K-Akt pathway. Thus inhibition of AR signalling and PI3K-Akt-mTOR (a downstream mediator of the PI3K-Akt pathway) pathway is a logical combination in CRPC and we report a phase II trial of RAD001 and bicalutamide. Our study is the first clinical trial report of an AR inhibitor of PI3K-Akt-mTOR. The AR pathway and the PI3K-Akt-mTOR pathway are two of the most relevant growth pathway for CRPC. Despite low efficacy results from our trial there will be significant interest in the field for these data (dose, schedule, response, toxicity, trial design) as newer generations of both AR inhibitors and PI3K-Akt-mTOR inhibitors are in development and likely will be tested in combination in CRPC.. • To determine best overall response and duration of response of RAD001, a selective inhibitor of mammalian target of rapamycin, in combination with bicalutamide in castration-resistant prostate cancer (CRPC). • To characterize the toxicity profile of RAD001 in combination with bicalutamide in patients with CRPC.. • A phase II study was conducted to explore the efficacy and tolerability of RAD001 (10 mg daily) in combination with bicalutamide (50 mg daily) in men with progressive CRPC. • The primary endpoint was a composite of prostate-specific antigen (PSA) level and measurable disease response by standard criteria. • This single-stage trial with a sample size of 38 eligible patients provided 90% power to differentiate a response rate of ≥ 40% from a response rate of ≤ 20%, as expected for bicalutamide alone (α= 0.10, power = 0.90).. • In total, 36 men were enrolled, with a median (range) age of 68 (60-72) years and median (range) baseline PSA level of 22.2 (8.4-121.3) ng/mL, and 89% had metastatic disease. • There were 31 (86%) patients had previously used bicalutamide for a median duration of 7.4 months. • There were two patients with a confirmed PSA level decline ≥ 50%. • The median (interquartile range) time to progression was 8.7 (7.9-15.9) weeks. • The most common toxicity was grade 1/2 mucositis, which was observed in 20 (56%) patients.. • The combination of RAD001 and bicalutamide in men with CRPC was well tolerated but had low activity and failed to achieve the primary endpoint of improved response compared to the results previously achieved for bicalutamide alone in this population.

Topics: Adenocarcinoma; Aged; Androgen Receptor Antagonists; Anilides; Antineoplastic Agents; Antineoplastic Combined Chemotherapy Protocols; Drug Resistance, Neoplasm; Everolimus; Humans; Male; Middle Aged; Nitriles; Prostate-Specific Antigen; Prostatic Neoplasms; Sirolimus; Tosyl Compounds; Treatment Outcome

The antiandrogen bicalutamide is widely used in the treatment of advanced prostate cancer (PCa) in many countries, but its effect on castration-resistant PCa (CRPC) is limited. We previously showed that resistance to bicalutamide results from activation of mechanistic target of rapamycin (mTOR). Interestingly, clinical trials testing combinations of the mTOR inhibitor RAD001 with bicalutamide were effective in bicalutamide-naïve CRPC patients, but not in bicalutamide-pretreated ones. Here we investigate causes for their difference in response. Evaluation of CRPC cell lines identified resistant vs sensitive in vitro models, and revealed that increased eIF4E(S209) phosphorylation is associated with resistance to the combination. We confirmed using a human-derived tumor xenograft mouse model that bicalutamide pre-treatment is associated with an increase in eIF4E(S209) phosphorylation. Thus, AR suppressed eukaryotic initiation factor 4E (eIF4E) phosphorylation, while the use of antiandrogens relieved this suppression, thereby triggering its increase. Additional investigation in human prostatectomy samples showed that increased eIF4E phosphorylation strongly correlated with the cell proliferation marker Ki67. Small interfering RNA-mediated knockdown (k/d) of eIF4E-sensitized CRPC cells to RAD001+bicalutamide, whereas eIF4E overexpression induced resistance. Inhibition of eIF4E phosphorylation by treatment with CGP57380 (an inhibitor of mitogen-activated protein kinase-interacting serine-threonine kinases MAP kinase-interacting kinase 1 (Mnk1/2), the eIF4E upstream kinase) or inhibitors of extracellular signal-regulated kinase 1/2 (ERK1/2), the upstream kinase-regulating Mnk1/2, also sensitized CRPC cells to RAD001+bicalutamide. Examination of downstream targets of eIF4E-mediated translation, including survivin, demonstrated that eIF4E(S209) phosphorylation increased cap-independent translation, whereas its inhibition restored cap-dependent translation, which could be inhibited by mTOR inhibitors. Thus, our results demonstrate that while combinations of AR and mTOR inhibitors were effective in suppressing tumor growth by inhibiting both AR-induced transcription and mTOR-induced cap-dependent translation, pre-treatment with AR antagonists including bicalutamide increased eIF4E phosphorylation that induced resistance to combinations of AR and mTOR inhibitors by inducing cap-independent translation. We conclude that this resistance can be overcome by inhibiting eI

Topics: Anilides; Aniline Compounds; Animals; Antineoplastic Combined Chemotherapy Protocols; Blotting, Western; Cell Line, Tumor; Eukaryotic Initiation Factor-4E; Everolimus; Humans; Intracellular Signaling Peptides and Proteins; Male; Mice, Nude; Nitriles; Phosphorylation; Prostatic Neoplasms, Castration-Resistant; Protein Serine-Threonine Kinases; Purines; Receptors, Androgen; Serine; Sirolimus; TOR Serine-Threonine Kinases; Tosyl Compounds; Xenograft Model Antitumor Assays

Although androgen ablation therapy is the foundation of current prostate cancer treatment, most patients ultimately develop castration-resistant disease. One proposed mechanism to account for androgen receptor (AR) activity in the castrate environment is via crosstalk with other signaling pathways. Specifically, reciprocal interactions between the AKT/mTOR and AR pathways have been implicated in prostate cancer progression. Here, we used the potent inhibitor ridaforolimus to target mTOR signaling alone and in combination with AR blockade by bicalutamide to examine the effect of abrogating these signaling pathways. Ridaforolimus treatment inhibited the proliferation of all six prostate cancer cell lines examined with the greatest sensitivity associated with loss of PTEN and elevated AKT/mTOR pathway activity. Dual inhibition of the AR and mTOR signaling pathways provided further benefit with the ridaforolimus-bicalutamide combination producing synergistic antiproliferative effects in prostate cancer cells in vitro when compared with each agent alone. Pharmacodynamic analysis confirmed that combination treatment resulted in full inhibition of each of the respective pathways. Importantly, the ridaforolimus-bicalutamide combination exhibited potent antitumor activity with parallel reductions in plasma PSA levels in vivo. Taken together, ridaforolimus exhibited potent antiproliferative and antitumor activity in prostate cancer models and the addition of bicalutamide represents a potentially effective combination strategy for patient therapy.

Topics: Androgen Receptor Antagonists; Anilides; Animals; Antineoplastic Combined Chemotherapy Protocols; Cell Cycle Checkpoints; Cell Line, Tumor; Cell Proliferation; Drug Synergism; Humans; Male; Mice; Mice, Nude; Nitriles; Prostate-Specific Antigen; Prostatic Neoplasms; PTEN Phosphohydrolase; Receptors, Androgen; Signal Transduction; Sirolimus; TOR Serine-Threonine Kinases; Tosyl Compounds; Tumor Burden; Xenograft Model Antitumor Assays

To determine the mechanisms associated with loss of androgen dependency and disease progression in prostate cancer (PCa), we investigated the relationship between the androgen receptor (AR) and mTOR pathways and the impact of inhibiting both pathways in androgen-dependent and castration-resistant PCa models.. Androgen-dependent (LNCaP) and castration-resistant PCa (HP-LNCaP) cells were grown as tumours in SCID mice. Once tumours reached 500 mm(3), animals were grouped and injected subcutaneous with vehicle, our novel anti-androgen/androgen synthesis inhibitor, VN/124-1, bicalutamide, and everolimus. Tumour volumes were measured biweekly. The PSA and protein analyses were performed after completion of the treatment.. The addition of everolimus to bicalutamide treatment of resistant tumours significantly reduced tumour growth rates and tumour volumes. Anti-androgen treatment also increased protein expression of multiple signal transduction pathways earlier than vehicle-treated control xenografts. VN/124-1 plus everolimus acted in concert to reduce tumour growth rates in our castration-resistant xenograft model.. This study suggests that dual inhibition of AR and mTOR in castration-resistant xenograft models can restore sensitivity of tumours to anti-androgen therapy. Furthermore, after bicalutamide failure, dual inhibition with VN/124-1 and everolimus was the most effective treatment.

Topics: Androgen Antagonists; Androgen Receptor Antagonists; Androstadienes; Anilides; Animals; Benzimidazoles; Castration; Cell Line, Tumor; Disease Progression; Drug Therapy, Combination; Everolimus; Intracellular Signaling Peptides and Proteins; Male; Mice; Mice, SCID; Neoplasms, Hormone-Dependent; Nitriles; Prostate-Specific Antigen; Prostatic Neoplasms; Protein Serine-Threonine Kinases; Receptor Cross-Talk; Signal Transduction; Sirolimus; TOR Serine-Threonine Kinases; Tosyl Compounds; Xenograft Model Antitumor Assays

Signaling between androgen receptor (AR) and mTOR may be crucial for prostate cancer cells to endure the low androgen and suboptimal nutrient conditions produced by androgen deprivation therapy.. AR and mTOR cross-talk was examined in LNCaP cells exposed to either high or low testosterone. AR and mTOR activities were modified separately using either siRNA knockdown or specific chemical inhibitor. The biological significance of the reciprocal communication was assessed by susceptibility to glucose deprivation-induced cell death.. AR positively regulated mTOR activity in both low and high testosterone levels. TSC1 and TSC2, the two negative regulators of mTOR, may be involved since both were up-regulated by AR knockdown. Sub-baseline mTOR increased AR protein levels. However, this effect only occurred with low testosterone. More cells underwent apoptosis if AR function was inhibited during glucose deprivation, which significantly depressed mTOR activity.. The compensatory increase of AR function due to a repressed mTOR signal is advantageous for survival. Disrupting this loop at the time of initiation of androgen deprivation therapy may delay, or even prevent, the recurrence of prostate cancer.

Topics: Androgen Antagonists; Anilides; Apoptosis; Cell Line, Tumor; Cell Survival; Down-Regulation; Gene Knockdown Techniques; Glucose; Humans; Male; Nitriles; Prostatic Neoplasms; Receptor Cross-Talk; Receptors, Androgen; RNA, Small Interfering; Sirolimus; Testosterone; TOR Serine-Threonine Kinases; Tosyl Compounds; Tuberous Sclerosis Complex 1 Protein; Tuberous Sclerosis Complex 2 Protein; Tumor Suppressor Proteins

In a previous report, we showed that increased activation of Akt, a downstream effector of phosphoinositide 3-kinase (PI3K) together with decreased activation of extracellular-signal-regulated kinase (ERK), a member of the mitogen-activated protein kinase (MAPK) family, predicted poor clinical outcome in prostate cancer (Kreisberg et al. 2004 Cancer Research 64 5232-5236). We now show that Akt activation, but not ERK activation, is correlated with proliferation in human prostate tumors as estimated by the expression of the cell proliferation antigen Ki67. We verified these results in vitro, using the androgen-dependent prostate cancer cell line LNCaP and its androgen-independent clone C4-2 as models of prostate cancer of good and poor clinical outcome, respectively. C4-2 cells expressed higher Akt activation, lower ERK activation and increased proliferation compared with LNCaP cells, similar to cases of poor clinical outcome. The PI3K inhibitor LY294002, but not the MAPK/ERK kinase inhibitor PD98059, induced growth arrest in both cell lines. Transient transfection with constitutively active Akt increased proliferation while dominant negative Akt decreased it, thus showing that Akt plays an important role in prostate cancer proliferation. Akt regulates the expression and activation of the androgen receptor. Androgen receptor inhibition with Casodex induced growth arrest in LNCaP cells, but not in C4-2 cells. Another PI3K downstream effector, p70 S6 kinase, requires prior phosphorylation by mammalian target of rapamycin (mTOR) for complete activation. Activation of p70 S6 kinase was higher in C4-2 compared with LNCaP cells. Rapamycin, an mTOR inhibitor, had a growth-inhibitory effect in C4-2 cells, but not in LNCaP cells. Our data suggest a shift from a Casodex-sensitive proliferation pathway in LNCaP cells to a rapamycin-sensitive pathway in C4-2 cells.

Topics: Androgen Antagonists; Androgen Receptor Antagonists; Androgens; Anilides; Antibiotics, Antineoplastic; Cell Proliferation; Enzyme Inhibitors; Humans; Ki-67 Antigen; Male; Mitogen-Activated Protein Kinases; Neoplasms, Hormone-Dependent; Nitriles; Phosphatidylinositol 3-Kinases; Phosphoinositide-3 Kinase Inhibitors; Phosphorylation; Prostatic Hyperplasia; Prostatic Intraepithelial Neoplasia; Prostatic Neoplasms; Protein Kinases; Protein Serine-Threonine Kinases; Proto-Oncogene Proteins; Proto-Oncogene Proteins c-akt; Receptors, Androgen; Ribosomal Protein S6 Kinases, 70-kDa; Signal Transduction; Sirolimus; TOR Serine-Threonine Kinases; Tosyl Compounds; Tumor Cells, Cultured