Pharmacogenomics with red cells: a model to study protein variants of drug transporter genes.

The PharmacoScan pharmacogenomics platform screens for variation in genes that affect drug absorption, distribution, metabolism, elimination, immune adverse reactions and targets. Among the 1,191 genes tested on the platform, 12 genes are expressed in the red cell membrane: ABCC1, ABCC4, ABCC5, ABCG2, CFTR, SLC16A1, SLC19A1, SLC29A1, ATP7A, CYP4F3, EPHX1 and FLOT1. These genes represent 5 ATP-binding cassette proteins, 3 solute carrier proteins, 1 ATP transport protein and 3 genes associated with drug metabolism and adverse drug reactions. Only ABCG2 and SLC29A1 encode blood group systems, JR and AUG, respectively. We propose red cells as an ex vivo model system to study the effect of heritable variants in genes encoding the transport proteins on the pharmacokinetics of drugs. Altered pharmacodynamics in red cells could also cause adverse reactions, such as haemolysis, hitherto unexplained by other mechanisms.

Phase 1 study of sorafenib and irinotecan in pediatric patients with relapsed or refractory solid tumors.

BACKGROUND: Sorafenib,an orally bioavailable, multitarget tyrosine kinase inhibitor, and irinotecan, a topoisomerase I inhibitor, have demonstrated activity in pediatric and adult malignancies. We evaluated the toxicity, pharmacokinetic (PK), and pharmacogenomic (PGX) profile of sorafenib with irinotecan in children with relapsed or refractory solid tumors and assessed the feasibility of incorporating patient-reported outcome (PRO) measures as an adjunct to traditional endpoints. METHODS: Sorafenib, continuous oral twice daily dosing, was administered with irinotecan, orally, once daily days 1-5, repeated every 21 days (NCT01518413). Based on tolerability, escalation of sorafenib followed by escalation of irinotecan was planned. Three patients were initially enrolled at each dose level. Sorafenib and irinotecan PK analyses were performed during cycle 1. PRO measurements were collected during cycles 1 and 2. RESULTS: Fifteen patients were evaluable. Two of three patients at dose level 2 experienced dose-limiting toxicity (DLT), grade 3 diarrhea, and grade 3 hyponatremia. Therefore, dose level 1 was expanded to 12 patients and two patients had DLT, grade 4 thrombocytopenia, grade 3 elevated lipase. Nine of 15 (60%) patients had a best response of stable disease with four patients receiving ≥6 cycles. CONCLUSIONS: The recommended dose for pediatric patients was sorafenib 150 mg/m2 /dose twice daily with irinotecan 70 mg/m2 /dose daily × 5 days every 21 days. This oral outpatient regimen was well tolerated and resulted in prolonged disease stabilization. There were no significant alterations in the PK profile of either agent when administered in combination. Patients were willing and able to report their subjective experiences with this regimen.

Cabozantinib in patients with platinum-refractory metastatic urothelial carcinoma: an open-label, single-centre, phase 2 trial.

BACKGROUND: Cabozantinib is a multikinase inhibitor of MET, VEGFR, AXL, and RET, which also has an effect on the tumour immune microenvironment by decreasing regulatory T cells and myeloid-derived suppressor cells. In this study, we examined the activity of cabozantinib in patients with metastatic platinum-refractory urothelial carcinoma. METHODS: This study was an open-label, single-arm, three-cohort phase 2 trial done at the National Cancer Institute (Bethesda, MD, USA). Eligible patients were 18 years or older, had histologically confirmed urothelial carcinoma or rare genitourinary tract histologies, Karnofsky performance scale index of 60% or higher, and documented disease progression after at least one previous line of platinum-based chemotherapy (platinum-refractory). Cohort one included patients with metastatic urothelial carcinoma with measurable disease as defined by Response Evaluation Criteria in Solid Tumors (RECIST) version 1.1. Two additional cohorts that enrolled in parallel (patients with bone-only urothelial carcinoma metastases and patients with rare histologies of the genitourinary tract) were exploratory. Patients received cabozantinib 60 mg orally once daily in 28-day cycles until disease progression or unacceptable toxicity. The primary endpoint was investigator-assessed objective response rate by RECIST in cohort one. Response was assessed in all patients who met the eligibility criteria and who received at least 8 weeks of therapy. All patients who received at least one dose of cabozantinib were included in the safety analysis. This completed study is registered with ClinicalTrials.gov, NCT01688999. FINDINGS: Between Sept 28, 2012, and Oct, 20, 2015, 68 patients were enrolled on the study (49 in cohort one, six in cohort two, and 13 in cohort three). All patients received at least one dose of cabozantinib. The median follow-up was 61·2 months (IQR 53·8-70·0) for the 57 patients evaluable for response. In the 42 evaluable patients in cohort one, there was one complete response and seven partial responses (objective response rate 19%, 95% CI 9-34). The most common grade 3-4 adverse events were fatigue (six [9%] patients), hypertension (five [7%]), proteinuria (four [6%]), and hypophosphataemia (four [6%]). There were no treatment-related deaths. INTERPRETATION: Cabozantinib has single-agent clinical activity in patients with heavily pretreated, platinum-refractory metastatic urothelial carcinoma with measurable disease and bone metastases and is generally well tolerated. Cabozantinib has innate and adaptive immunomodulatory properties providing a rationale for combining cabozantinib with immunotherapeutic strategies. FUNDING: National Cancer Institute Intramural Program and the Cancer Therapy Evaluation Program.

Comparison of Eight Technologies to Determine Genotype at the UGT1A1 (TA)n Repeat Polymorphism: Potential Clinical Consequences of Genotyping Errors?

To ensure accuracy of UGT1A1 (TA)n (rs3064744) genotyping for use in pharmacogenomics-based irinotecan dosing, we tested the concordance of several commonly used genotyping technologies. Heuristic genotype groupings and principal component analysis demonstrated concordance for Illumina sequencing, fragment analysis, and fluorescent PCR. However, Illumina sequencing and fragment analysis returned a range of fragment sizes, likely arising due to PCR "slippage". Direct sequencing was accurate, but this method led to ambiguous electrophoregrams, hampering interpretation of heterozygotes. Gel sizing, pyrosequencing, and array-based technologies were less concordant. Pharmacoscan genotyping was concordant, but it does not ascertain (TA)8 genotypes that are common in African populations. Method-based genotyping differences were also observed in the publication record (p < 0.0046), although fragment analysis and direct sequencing were concordant (p = 0.11). Genotyping errors can have significant consequences in a clinical setting. At the present time, we recommend that all genotyping for this allele be conducted with fluorescent PCR (fPCR).

Severe Hepatotoxicity of Mithramycin Therapy Caused by Altered Expression of Hepatocellular Bile Transporters.

Mithramycin demonstrates preclinical anticancer activity, but its therapeutic dose is limited by the development of hepatotoxicity that remains poorly characterized. A pharmacogenomics characterization of mithramycin-induced transaminitis revealed that hepatotoxicity is associated with germline variants in genes involved in bile disposition: ABCB4 (multidrug resistance 3) rs2302387 and ABCB11 [bile salt export pump (BSEP)] rs4668115 reduce transporter expression (P < 0.05) and were associated with ≥grade 3 transaminitis developing 24 hours after the third infusion of mithramycin (25 mcg/kg, 6 hours/infusion, every day ×7, every 28 days; P < 0.0040). A similar relationship was observed in a pediatric cohort. We therefore undertook to characterize the mechanism of mithramycin-induced acute transaminitis. As mithramycin affects cellular response to bile acid treatment by altering the expression of multiple bile transporters (e.g., ABCB4, ABCB11, sodium/taurocholate cotransporting polypeptide, organic solute transporter α/ß) in several cell lines [Huh7, HepaRG, HepaRG BSEP (-/-)] and primary human hepatocytes, we hypothesized that mithramycin inhibited bile-mediated activation of the farnesoid X receptor (FXR). FXR was downregulated in all hepatocyte cell lines and primary human hepatocytes (P < 0.0001), and mithramycin inhibited chenodeoxycholic acid- and GW4046-induced FXR-galactose-induced gene 4 luciferase reporter activity (P < 0.001). Mithramycin promoted glycochenodeoxycholic acid-induced cytotoxicity in ABCB11 (-/-) cells and increased the overall intracellular concentration of bile acids in primary human hepatocytes grown in sandwich culture (P < 0.01). Mithramycin is a FXR expression and FXR transactivation inhibitor that inhibits bile flow and potentiates bile-induced cellular toxicity, particularly in cells with low ABCB11 function. These results suggest that mithramycin causes hepatotoxicity through derangement of bile acid disposition; results also suggest that pharmacogenomic markers may be useful to identify patients who may tolerate higher mithramycin doses. SIGNIFICANCE STATEMENT: The present study characterizes a novel mechanism of drug-induced hepatotoxicity in which mithramycin not only alters farnesoid X receptor (FXR) and small heterodimer partner gene expression but also inhibits bile acid binding to FXR, resulting in deregulation of cellular bile homeostasis. Two novel single-nucleotide polymorphisms in bile flow transporters are associated with mithramycin-induced liver function test elevations, and the present results are the rationale for a genotype-directed clinical trial using mithramycin in patients with thoracic malignancies.

Pilot Study Comparing Systemic and Tissue Pharmacokinetics of Irinotecan and Metabolites after Hepatic Drug-Eluting Chemoembolization.

Differences in drug metabolism associated with UGT1A1 polymorphism could result in individualized local response to hepatic chemoembolization with irinotecan-eluting beads (DEBIRI) or predictable toxicities. Five patients with inoperable hepatic metastases from colorectal or anal malignancies treated with DEBIRI were assessed for UGT1A1 mutations. No difference in area under the curve (AUC) for SN38 in normal liver and tumor tissue samples was noted with variant or wild-type UBT1A1 (P = .16 and P = .05, respectively). Plasma SN-38 AUC was significantly lower in wild-type compared to variant patients (P < .0001). UGT1A1 genotype may not be predictive of hematologic toxicity after DEBIRI.

Phase II trial of docetaxel, bevacizumab, lenalidomide and prednisone in patients with metastatic castration-resistant prostate cancer.

OBJECTIVE: To determine the safety and clinical efficacy of two anti-angiogenic agents, bevacizumab and lenalidomide, with docetaxel and prednisone. PATIENTS AND METHODS: Eligible patients with metastatic castration-resistant prostate cancer enrolled in this open-label, phase II study of lenalidomide with bevacizumab (15 mg/kg), docetaxel (75 mg/m(2) ) and prednisone (10 mg daily). Docetaxel and bevacizumab were administered on day 1 of a 3-week treatment cycle. To establish safety, lenalidomide dosing in this combination was escalated in a conventional 3 + 3 design (15, 20 and 25 mg daily for 2 weeks followed by 1 week off). Patients received supportive measures including prophylactic pegfilgrastim and enoxaparin. The primary endpoints were safety and clinical efficacy. RESULTS: A total of 63 patients enrolled in this trial. Toxicities were manageable with most common adverse events (AEs) being haematological, and were ascertained by weekly blood counts. Twenty-nine patients (46%) had grade 4 neutropenia, 20 (32%) had grade 3 anaemia and seven (11%) had grade 3 thrombocytopenia. Despite frequent neutropenia, serious infections were rare. Other common non-haematological grade 3 AEs included fatigue (10%) and diarrhoea (10%). Grade 2 AEs in >10% of patients included anorexia, weight loss, constipation, osteonecrosis of the jaw, rash and dyspnoea. Of 61 evaluable patients, 57 (93%), 55 (90%) and 33 (54%) had PSA declines of >30, >50 and >90%, respectively. Of the 29 evaluable patients, 24 (86%) had a confirmed radiographic partial response. The median times to progression and overall survival were 18.2 and 24.6 months, respectively. CONCLUSIONS: With appropriate supportive measures, combination angiogenesis inhibition can be safely administered and potentially provide clinical benefit. These hypothesis-generating data would require randomized trials to confirm the findings.

Androgen receptor variation affects prostate cancer progression and drug resistance.

Significant therapeutic progress has been made in treating prostate cancer in recent years. Drugs such as enzalutamide, abiraterone, and cabazitaxel have expanded the treatment armamentarium, although it is not completely clear which of these drugs are the most-effective option for individual patients. Moreover, such advances have been tempered by the development of therapeutic resistance. The purpose of this review is to summarize the current literature pertaining to the biochemical effects of AR variants and their consequences on prostate cancer therapies at both the molecular level and in clinical treatment. We address how these AR splice variants and mutations affect tumor progression and therapeutic resistance and discuss potential novel therapeutic strategies under development. It is hoped that these therapies can be administered with increasing precision as tumor genotyping methods become more sophisticated, thereby lending clinicians a better understanding of the underlying biology of prostate tumors in individual patients.

Screening and Biological Effects of Marine Pyrroloiminoquinone Alkaloids: Potential Inhibitors of the HIF-1α/p300 Interaction.

Inhibition of the hypoxia-inducible factor 1α (HIF-1α) pathway by disrupting its association with the transcriptional coactivator p300 inhibits angiogenesis and tumor development. Development of HIF-1α/p300 inhibitors has been hampered by preclinical toxicity; therefore, we aimed to identify novel HIF-1α/p300 inhibitors. Using a cell-free assay designed to test compounds that block HIF-1α/p300 binding, 170 298 crude natural product extracts and prefractionated samples were screened, identifying 25 active extracts. One of these extracts, originating from the marine sponge Latrunculia sp., afforded six pyrroloiminoquinone alkaloids that were identified as positive hits (IC50 values: 1-35 µM). Luciferase assays confirmed inhibition of HIF-1α transcriptional activity by discorhabdin B (1) and its dimer (2), 3-dihydrodiscorhabdin C (3), makaluvamine F (5), discorhabdin H (8), discorhabdin L (9), and discorhabdin W (11) in HCT 116 colon cancer cells (0.1-10 µM, p < 0.05). Except for 11, all of these compounds also reduced HIF-1α transcriptional activity in LNCaP prostate cancer cells (0.1-10 µM, p < 0.05). These effects occurred at noncytotoxic concentrations (<50% cell death) under hypoxic conditions. At the downstream HIF-1α target level, compound 8 (0.5 µM) significantly decreased VEGF secretion in LNCaP cells (p < 0.05). In COLO 205 colon cancer cells no activity was shown in the luciferase or cytotoxicity assays. Pyrroloiminoquinone alkaloids are a novel class of HIF-1α inhibitors, which interrupt the protein-protein interaction between HIF-1α and p300 and consequently reduce HIF-related transcription.

Dual targeting of the androgen receptor and hypoxia-inducible factor 1α pathways synergistically inhibits castration-resistant prostate cancer cells.

Enzalutamide is a potent second-generation androgen receptor (AR) antagonist with activity in metastatic castrate-resistant prostate cancer (CRPC). Although enzalutamide is initially effective, disease progression inevitably ensues with the emergence of resistance. Intratumoral hypoxia is also associated with CRPC progression and treatment resistance. Given that both AR and hypoxia inducible factor-1 α (HIF-1α) are key regulators of these processes, dual targeting of both signaling axes represents an attractive therapeutic approach. Crosstalk of the AR and HIF-1α signaling pathways were examined in prostate cancer cell lines (LNCaP, 22Rv1) with assays measuring the effect of androgen and hypoxia on AR-dependent and hypoxia-inducible gene transcription, protein expression, cell proliferation, and apoptosis. HIF-1α inhibition was achieved by siRNA silencing HIF-1α or via chetomin, a disruptor of HIF-1α-p300 interactions. In prostate cancer cells, the gene expression of AR targets (KLK3, FKBP5, TMPRSS2) was repressed by HIF-signaling; conversely, specific HIF-1α target expression was induced by dihydrotestosterone-mediated AR signaling. Treatment of CRPC cells with enzalutamide or HIF-1α inhibition attenuated AR-regulated and HIF-1α-mediated gene transcription. The combination of enzalutamide and HIF-1α inhibition was more effective than either treatment alone. Similarly, the combination also reduced vascular endothelial growth factor protein levels. HIF-1α siRNA synergistically enhanced the inhibitory effect of enzalutamide on cell growth in LNCaP and enzalutamide-resistant 22Rv1 cells via increased enzalutamide-induced apoptosis. In conclusion, the combination of enzalutamide with HIF-1α inhibition resulted in synergistic inhibition of AR-dependent and gene-specific HIF-dependent expression and prostate cancer cell growth.

Genetic variation: effect on prostate cancer.

The crucial role of androgens in the development of prostate cancer is well established. The aim of this review is to examine the role of constitutional (germline) and tumor-specific (somatic) polymorphisms within important regulatory genes of prostate cancer. These include genes encoding enzymes of the androgen biosynthetic pathway, the androgen receptor gene, genes that encode proteins of the signal transduction pathways that may have a role in disease progression and survival, and genes involved in prostate cancer angiogenesis. Characterization of deregulated pathways critical to cancer cell growth have lead to the development of new treatments, including the CYP17 inhibitor abiraterone and clinical trials using novel drugs that are ongoing or recently completed [1]. The pharmacogenetics of the drugs used to treat prostate cancer will also be addressed. This review will define how germline polymorphisms are known affect a multitude of pathways, and therefore phenotypes, in prostate cancer etiology, progression, and treatment.

Phase 1 trial and pharmacokinetic study of the oral platinum analog satraplatin in children and young adults with refractory solid tumors including brain tumors.

BACKGROUND: Based on pre-clinical and clinical activity in adult refractory tumors, and absence of significant neuro-, nephro-, or oto-toxicity, we conducted a pediatric phase 1 trial to determine the toxicities, maximum tolerated dose (MTD), and pharmacokinetics of satraplatin, an oral platinum analogue, in children and young adults with refractory solid tumors. PROCEDURE: Satraplatin was administered orally once daily on days 1-5 of a 28-day cycle at dose level (DL) 1 (60 mg/m(2) /dose), and DL2 (80 mg/m(2) /dose). Toxicities, responses, satraplatin pharmacokinetics, and pharmacogenomic expression of specific DNA repair genes were evaluated. RESULTS: Nine patients received 1-15 cycles (median = 2). The MTD was exceeded at DL2 with delayed prolonged myelosuppression as dose-limiting toxicity (DLT) in 2/4 patients. At DL1, 0/5 patients had DLTs. Common non-DLTs included myelosuppression, gastrointestinal toxicities, fatigue, headache, liver enzyme elevation, and electrolyte abnormalities. No significant neuro-, nephro-, or oto-toxicity was observed. No objective responses were observed but 2 patients experienced prolonged disease stabilization (---6-15 cycles). Satraplatin exposure (day 1 plasma ultrafiltrate area under the curve) was similar at DL1 and DL2. A strong correlation between estimated creatinine clearance and satraplatin pharmacokinetic parameters (clearance, area under the curve, and peak concentration) was observed. CONCLUSIONS: The MTD of oral satraplatin in children with solid tumors was 60 mg/m(2) /dose daily ×5 days every 28 days, which is lower than the adult recommended dose of 80-120 mg/m(2) /dose. The toxicity profile was similar to adults and delayed myelosuppression was the DLT. No significant neuro-, nephro- or oto-toxicities were observed.

GNRH2 Polymorphism in Men With Prostate Cancer Treated With Androgen Deprivation Therapy.

BACKGROUND/AIM: Gonadotropin-releasing hormone 2 (GNRH2) is a poorly-studied peptide hormone that is widely distributed in the central nervous system and expressed in peripheral tissues of mammals. The non-synonymous rs6051545 variant in GNRH2 (A16V) has been linked to higher serum testosterone concentrations. This study investigated whether the A16V variant is associated with altered androgen-deprivation therapy (ADT) progression-free survival (PFS) and overall survival (OS). PATIENTS AND METHODS: We examined the expression of GNRH2 in prostate tissue microarrays comprising normal tissue, prostatic hyperplasia, and prostate cancer using immunofluorescence. We also evaluated the GNRH2 genotype in 131 patients with prostate cancer who received ADT and compared PFS and OS between the variant and wild-type genotypes. RESULTS: GNRH2 was detected in all prostate tissues, although expression did not vary with Gleason grade or disease stage (p=0.71). The GNRH2 A16V genotype was not associated with PFS or OS; however, univariate and multivariate analyses revealed Gleason score and definitive local therapy were each associated with PFS (p≤0.0074), whereas age and Gleason score were associated with OS (p≤0.0046). CONCLUSION: GNRH2 is expressed in normal, hyperplastic, and neoplastic prostate tissues; the A16V variant is not related to treatment outcome or survival.

Targeting Replication Stress and Chemotherapy Resistance with a Combination of Sacituzumab Govitecan and Berzosertib: A Phase I Clinical Trial.

PURPOSE: Despite promising preclinical studies, toxicities have precluded combinations of chemotherapy and DNA damage response (DDR) inhibitors. We hypothesized that tumor-targeted chemotherapy delivery might enable clinical translation of such combinations. PATIENTS AND METHODS: In a phase I trial, we combined sacituzumab govitecan, antibody-drug conjugate (ADC) that delivers topoisomerase-1 inhibitor SN-38 to tumors expressing Trop-2, with ataxia telangiectasia and Rad3-related (ATR) inhibitor berzosertib. Twelve patients were enrolled across three dose levels. RESULTS: Treatment was well tolerated, with improved safety over conventional chemotherapy-based combinations, allowing escalation to the highest dose. No dose-limiting toxicities or clinically relevant ≥grade 4 adverse events occurred. Tumor regressions were observed in 2 patients with neuroendocrine prostate cancer, and a patient with small cell lung cancer transformed from EGFR-mutant non-small cell lung cancer. CONCLUSIONS: ADC-based delivery of cytotoxic payloads represents a new paradigm to increase efficacy of DDR inhibitors. See related commentary by Berg and Choudhury, p. 3557.