Efficacy and safety of isatuximab plus bortezomib, lenalidomide, and dexamethasone in patients with newly diagnosed multiple myeloma ineligible/with no immediate intent for autologous stem cell transplantation.

Patients with newly diagnosed multiple myeloma (NDMM) ineligible for autologous stem cell transplantation (ASCT) have lower survival rates and may benefit from frontline regimens that include novel agents. This Phase 1b study (NCT02513186) evaluated preliminary efficacy, safety, and pharmacokinetics (PK) of isatuximab, an anti-CD38 monoclonal antibody, combined with bortezomib-lenalidomide-dexamethasone (Isa-VRd) in patients with NDMM ineligible for/with no intent for immediate ASCT. Overall, 73 patients received four 6-week induction cycles of Isa-VRd, then maintenance with Isa-Rd in 4-week cycles. In the efficacy population (n = 71), the overall response rate was 98.6%, with 56.3% achieving a complete response or better (sCR/CR), and 36/71 (50.7%) patients reaching minimal residual disease negativity (10-5 sensitivity). Grade ≥3 treatment-emergent adverse events (TEAEs) occurred in 79.5% (58/73) of patients but TEAEs leading to permanent study treatment discontinuation were reported in 14 (19.2%) patients. Isatuximab PK parameters were within the previously reported range, suggesting that VRd does not alter the PK of isatuximab. These data support additional studies of isatuximab in NDMM, such as the Phase 3 IMROZ study (Isa-VRd vs VRd).

PXR Modulates the Prostate Cancer Cell Response to Afatinib by Regulating the Expression of the Monocarboxylate Transporter SLC16A1.

Resistance to castration is a crucial issue in the treatment of metastatic prostate cancer. Kinase inhibitors (KIs) have been tested as potential alternatives, but none of them are approved yet. KIs are subject of extensive metabolism at both the hepatic and the tumor level. Here, we studied the role of PXR (Pregnane X Receptor), a master regulator of metabolism, in the resistance to KIs in a prostate cancer setting. We confirmed that PXR is expressed in prostate tumors and is more frequently detected in advanced forms of the disease. We showed that stable expression of PXR in 22Rv1 prostate cancer cells conferred a resistance to dasatinib and a higher sensitivity to erlotinib, dabrafenib, and afatinib. Higher sensitivity to afatinib was due to a ~ 2-fold increase in its intracellular accumulation and involved the SLC16A1 transporter as its pharmacological inhibition by BAY-8002 suppressed sensitization of 22Rv1 cells to afatinib and was accompanied with reduced intracellular concentration of the drug. We found that PXR could bind to the SLC16A1 promoter and induced its transcription in the presence of PXR agonists. Together, our results suggest that PXR could be a biomarker of response to kinase inhibitors in castration-resistant prostate cancers.

The Anti-Cancer Drug Dabrafenib Is a Potent Activator of the Human Pregnane X Receptor.

The human pregnane X receptor (hPXR) is activated by a large set of endogenous and exogenous compounds and plays a critical role in the control of detoxifying enzymes and transporters regulating liver and gastrointestinal drug metabolism and clearance. hPXR is also involved in both the development of multidrug resistance and enhanced cancer cells aggressiveness. Moreover, its unintentional activation by pharmaceutical drugs can mediate drug-drug interactions and cause severe adverse events. In that context, the potential of the anticancer BRAF inhibitor dabrafenib suspected to activate hPXR and the human constitutive androstane receptor (hCAR) has not been thoroughly investigated yet. Using different reporter cellular assays, we demonstrate that dabrafenib can activate hPXR as efficiently as its reference agonist SR12813, whereas it does not activate mouse or zebrafish PXR nor hCAR. We also showed that dabrafenib binds to recombinant hPXR, induces the expression of hPXR responsive genes in colon LS174T-hPXR cancer cells and human hepatocytes and finally increases the proliferation in LS174T-hPXR cells. Our study reveals that by using a panel of different cellular techniques it is possible to improve the assessment of hPXR agonist activity for new developed drugs.

Association of NR1I2, CYP3A5 and ABCB1 genetic polymorphisms with variability of temsirolimus pharmacokinetics and toxicity in patients with metastatic bladder cancer.

PURPOSE: Temsirolimus is a mammalian target of rapamycin (mTOR) inhibitor that exhibits antitumor activity in renal cell carcinoma and mantle cell lymphoma. The metabolism of temsirolimus and its active metabolite sirolimus mainly depends on cytochrome P450 3A4/5 (CYP3A4/A5) and the ABCB1 transporter. Differently from sirolimus, no pharmacogenetic study on temsirolimus has been conducted. Therefore, the aim of this pilot study was to identify genetic determinants of the inter-individual variability in temsirolimus pharmacokinetics and toxicity. METHODS: Pharmacokinetic profiles were obtained for 16 patients with bladder cancer after intravenous infusion of 25 mg temsirolimus. Non-compartmental analysis was performed to calculate the pharmacokinetic parameters of temsirolimus and sirolimus, its main metabolite. The presence of single nucleotide polymorphisms (SNPs) in CYP3A5, ABCB1 and in their transcriptional regulator NR1I2 (PXR) was assessed by genotyping. Non-parametric statistical tests were used to assess associations between candidate SNPs and temsirolimus pharmacokinetics and toxicity. RESULTS: The ratio between sirolimus AUC and temsirolimus AUC was 1.6-fold higher in patients who experienced serious toxic events (p = 0.034). The frequency of adverse events was significantly higher in patients homozygous for the NR1I2-rs6785049 A allele (OR = 0.065, p = 0.04) or NR1I2-rs3814055 C allele (OR = 0.032, p = 0.006). These NR1I2 SNPs were also predictive of temsirolimus half-life and global exposure to temsirolimus and sirolimus. Finally, the effect of the ABCB1-rs1128503, ABCB1-rs2032582 and CYP3A5*3 SNPs on sirolimus pharmacokinetics was confirmed. CONCLUSIONS: Our findings suggest that SNPs of NR1I2 and its target genes CYP3A5 and ABCB1 are genetic determinants of temsirolimus pharmacokinetics and toxicity in patients with bladder cancer.

Effect of Single Nucleotide Polymorphisms in the Xenobiotic-sensing Receptors NR1I2 and NR1I3 on the Pharmacokinetics and Toxicity of Irinotecan in Colorectal Cancer Patients.

BACKGROUND AND OBJECTIVES: Nuclear receptors PXR (pregnane X receptor, NR1I2) and CAR (constitutive androstane receptor, NR1I3) are key regulators of irinotecan metabolism, and ligand-dependent modulation of their activity leads to significant drug-drug interactions. Because genetic polymorphisms can also affect the activity of these xenobiotic-sensing receptors, we hypothesized that they could contribute to the interpatient variability of irinotecan pharmacokinetics and to the toxicity of irinotecan-based regimens. PATIENTS AND METHODS: In a cohort of 109 metastatic colorectal cancer patients treated with irinotecan (180 mg/m(2)) in combination with other drugs, associations were assessed between 21 selected single nucleotide polymorphisms of NR1I2 or NR1I3 and pharmacokinetic parameters or toxicity of irinotecan and its metabolites. RESULTS: After adjustment of the tests by the UGT1A1*28 genotype and correction for multiple testing, the A allele of NR1I2-rs10934498 was associated with a decreased exposition and an increased degradation of SN-38, the active metabolite (p = 0.009 and p = 0.017, respectively). The risk of hematological toxicity was associated with NR1I2-rs10934498 and NR1I2-rs2472677 (p = 0.009 and p = 0.003, respectively). CONCLUSION: Our results reveal for the first time the involvement of NR1I2 in the pharmacogenetics of irinotecan and suggest that it may help to predict the toxicity of low-dose irinotecan.