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Biomedical subjects

Alan P Venook

Publications and source records attributed to Alan P Venook.

At least 19 recordsLinked to original sources
PubMed2025

Expansion of a bacterial operon during cancer treatment ameliorates fluoropyrimidine toxicity.

Dose-limiting toxicities remain a major barrier to drug development and therapy, revealing the limited predictive power of human genetics. Here, we demonstrate the utility of a more comprehensive approach to studying drug toxicity through longitudinal profiling of the human gut microbiome during colorectal cancer (CRC) treatment (NCT04054908) coupled to cell culture and mouse experiments. Substantial shifts in gut microbial community structure during oral fluoropyrimidine treatment across multiple patient cohorts, in mouse small and large intestinal contents, and in patient-derived ex vivo communities were revealed by 16S rRNA gene sequencing. Metagenomic sequencing revealed marked shifts in pyrimidine-related gene abundance during oral fluoropyrimidine treatment, including enrichment of the preTA operon, which was sufficient for the inactivation of active metabolite 5-fluorouracil (5-FU). preTA+ bacteria depleted 5-FU in gut microbiota grown ex vivo and in the mouse distal gut. Germ-free and antibiotic-treated mice experienced increased fluoropyrimidine toxicity, which was rescued by colonization with the mouse gut microbiota, preTA+ Escherichia coli, or preTA-high stool from patients with CRC. Last, preTA abundance was negatively associated with fluoropyrimidine toxicity in patients. Together, these data support a causal, clinically relevant interaction between a human gut bacterial operon and the dose-limiting side effects of cancer treatment. Our approach may be generalizable to other drugs, including cancer immunotherapies, and provides valuable insights into host-microbiome interactions in the context of disease.

Animals↗
PubMed2006

Phase II study of recombinant human endostatin in patients with advanced neuroendocrine tumors.

PURPOSE: Endostatin is a 20-kd proteolytic fragment of collagen XVIII that, in preclinical studies, has been shown to have antiangiogenic and antitumor activity. Both preclinical and human phase I studies of recombinant human endostatin (rhEndostatin) suggested activity in neuroendocrine tumors, which are known to be hypervascular. We therefore performed a multicenter phase II study of rhEndostatin in patients with carcinoid or pancreatic neuroendocrine tumors. PATIENTS AND METHODS: Forty-two patients with advanced pancreatic endocrine tumors or carcinoid tumors were treated with rhEndostatin administered as a bid subcutaneous injection at a starting dose of 60 mg/m2/d. Steady-state trough levels were obtained after 6 weeks of therapy; patients who did not achieve a target therapeutic level of 300 ng/mL underwent dose escalation to 90 mg/m2/d. Patients were observed for evidence of toxicity, response, and survival. RESULTS: rhEndostatin was associated with minimal toxicity. However, among 40 patients assessable for radiologic response, none experienced partial response to therapy, as defined by WHO criteria. The median steady-state trough level achieved after dose escalation was 331 ng/mL, within the postulated therapeutic range. CONCLUSION: Treatment with rhEndostatin did not result in significant tumor regression in patients with advanced neuroendocrine tumors.

Adult↗
PubMed2006

The cancer and leukemia group B pharmacology and experimental therapeutics committee: a historical perspective.

The Chemotherapy Committee of Cancer and Leukemia Group B (CALGB) was established in the mid-1970s to assemble a group of experts in cancer chemotherapy and pharmacology who could advise the CALGB disease committees about the optimal use of drugs in the fight against cancer and to provide quality assurance for the chemotherapy section of CALGB protocols. Chaired initially by Edward Henderson and then David Van Echo, the committee was also the repository of studies in diseases for which CALGB did not have a formal committee, such as testis cancer and sarcoma. In 1990, following the appointment of Richard Schilsky as Chair, the name of the committee was changed to the Pharmacology and Experimental Therapeutics (PET) Committee to reflect a more specific focus and scientific agenda (i.e., studies of chemotherapy pharmacology and development of new agents). Three PET Committee reference pharmacology laboratories (led by Merrill Egorin, Tony Miller, and Mark Ratain) were established to measure drug concentrations in biological fluids and to perform pharmacokinetic analyses. In addition, the PET Committee embarked on a number of multi-institution phase I studies. These phase I studies included studies of special populations, including the first prospective study of an anticancer agent (paclitaxel) in patients with hepatic dysfunction. In addition, the Committee studied a number of phase I combinations destined for phase II evaluation in disease-specific committees. Following Dr. Schilsky's election as CALGB Group Chair in 1994, Mark Ratain took over as Chair of the PET Committee and continued to emphasize population pharmacology as the primary theme of the Committee's research agenda. In addition, the PET Committee began to develop novel clinical trial designs, including the first completed randomized discontinuation trial of an antineoplastic agent. Most recently, the PET Committee has launched an ambitious research program in pharmacogenetics, facilitated in large part through the recruitment of Howard McLeod as Vice Chair. This area of research is a collaborative effort with the NIH Pharmacogenetics Research Network and has the potential to definitively address the hypothesis that germ line polymorphisms are a significant determinant of the toxicity and efficacy of anticancer therapy. It is anticipated that the results of the current studies will contribute significantly to the goal of individualizing cancer treatment.

Antineoplastic Agents↗
PubMed2006

Targeted therapy in colorectal cancer.

Advances in chemotherapeutic agents have led to improved outcomes for patients with metastatic colorectal cancer (CRC). Chemotherapies, however, are limited by their toxicities and lack of specificity. Aberrations in the regulation and expression of growth factors have been implicated in the development of CRC, and this understanding has led to the development of targeted agents. In 2004, two novel agents, bevacizumab and cetuximab, were approved by the US Food and Drug Administration for the treatment of metastatic CRC. Bevacizumab, a humanized monoclonal antibody to vascular endothelial growth factor, and cetuximab, a human-mouse chimeric monoclonal antibody to the epidermal growth factor receptor, have changed the field dramatically. Bevacizumab appears to augment the efficacy of combination chemotherapy regimens for the treatment of metastatic CRC in both the first- and second-line settings, and the role of bevacizumab as part of adjuvant treatment is the subject of ongoing trials. However, because of the increased incidence of serious arterial thromboembolic events, gastrointestinal perforations, bleeding complications, and hypertension associated with bevacizumab, this agent is probably not indicated in all circumstances. Combination treatment with cetuximab and irinotecan appears appropriate in patients with advanced CRC who have failed irinotecan. Patients who are unable to receive additional irinotecan may be treated with cetuximab monotherapy. Positive epidermal growth factor receptor status by immunohistochemistry of a tumor specimen is presently mandated to determine candidacy for this therapy, although this assay appears to be suboptimal and newer assessment techniques to determine suitability for therapy must be developed. Phase III trials should shed light on the role of cetuximab in the first-line metastatic and adjuvant settings. Multitargeted strategies in CRC combining chemotherapy with bevacizumab and cetuximab are currently being explored. Further advances in the treatment of CRC are expected through continued scientific investigation and well-designed clinical trials.

Antibodies, Monoclonal↗
PubMed2005

Phase II study of fixed dose rate gemcitabine with cisplatin for metastatic adenocarcinoma of the pancreas.

PURPOSE: Although gemcitabine remains the standard of care for patients with advanced pancreatic cancer, additional improvements may be realized by combining therapeutic agents with synergistic activity, and optimizing drug delivery using pharmacokinetic principles such as fixed dose rate (FDR) infusion. The objectives of this study were to determine safety and efficacy in patients with metastatic pancreatic cancer treated with FDR gemcitabine in combination with low-dose cisplatin. PATIENTS AND METHODS: Chemotherapy-naive patients with metastatic pancreatic adenocarcinoma were treated with a combination of gemcitabine 1,000 mg/m2 at 10 mg/m2/min together with cisplatin 20 mg/m2 on days 1 and 8 of a 21-day cycle. Patient follow-up was performed using computerized tomographic scans and serial CA 19-9 measurements. RESULTS: A total of 51 patients were enrolled onto the study, with a median follow-up time of 215 days. Twenty-two of 40 patients (55.0%) with a baseline serum CA 19-9 level > or = 2x the upper limit of normal demonstrated a > or = 50% biomarker decline during treatment. Nine of 47 patients (19.1%) with measurable disease achieved a partial response, and 28 patients (59.6%) had disease stabilization for at least two treatment cycles. Median time to progression was 3.9 months and median survival was 7.1 months, with an estimated 1-year survival rate of 29%. The most frequently reported grade 3 or 4 adverse events were neutropenia (52.9%) and thrombocytopenia (15.7%). Most patients were switched to an every-other-week dosing schedule. CONCLUSION: The combination of FDR gemcitabine and cisplatin is well tolerated and appears to be an acceptable, albeit not clearly superior, alternative to other gemcitabine/platinum regimens for the treatment of metastatic pancreatic cancer.

Adenocarcinoma↗
PubMed2005

Epidermal growth factor receptor-targeted treatment for advanced colorectal carcinoma.

Substantial effort has focused on the development of novel targeted agents for treating patients with late-stage colorectal carcinoma. These agents are designed specifically to inhibit biochemical processes associated with pathogenesis. Numerous molecules targeting the epidermal growth factor receptor have been investigated as therapeutic agents and appear to herald a shift in the treatment paradigm for colorectal carcinoma.

Antibodies, Monoclonal↗
PubMed2005

Fractional genomic alteration detected by array-based comparative genomic hybridization independently predicts survival after hepatic resection for metastatic colorectal cancer.

PURPOSE: Although liver resection is the primary curative therapy for patients with colorectal hepatic metastases, most patients have a recurrence. Identification of molecular markers that predict patients at highest risk for recurrence may help to target further therapy. EXPERIMENTAL DESIGN: Array-based comparative genomic hybridization was used to investigate the association of DNA copy number alterations with outcome in patients with colorectal liver metastasis resected with curative intent. DNA from 50 liver metastases was labeled and hybridized onto an array consisting of 2,463 bacterial artificial chromosome clones covering the entire genome. The total fraction of genome altered (FGA) in the metastases and the patient's clinical risk score (CRS) were calculated to identify independent prognostic factors for survival. RESULTS: An average of 30 +/- 14% of the genome was altered in the liver metastases (14% gained and 16% lost). As expected, a lower CRS was an independent predictor of overall survival (P = 0.03). In addition, a high FGA also was an independent predictor of survival (P = 0.01). The median survival time in patients with a low CRS (score 0-2) and a high (> or =20%) FGA was 38 months compared with 18 months in patients with a low CRS and a low FGA. Supervised analyses, using Prediction Analysis of Microarrays and Significance Analysis of Microarrays, identified a set of clones, predominantly located on chromosomes 7 and 20, which best predicted survival. CONCLUSIONS: Both FGA and CRS are independent predictors of survival in patients with resected hepatic colorectal cancer metastases. The greater the FGA, the more likely the patient is to survive.

Aged↗
PubMed2004

Key research issues in the management of hepatocellular carcinoma.

Hepatocellular carcinoma (HCC) is an extremely diverse and heterogeneous disease and improving patient outcome is a difficult undertaking. While many therapeutic options exist, few have been subjected to rigorous study, so patient benefit is uncertain. Comparative trials need to be performed to determine the value of these and, of course, newer treatments. However, there are numerous challenges to the design and conduct of such studies. While stratification parameters are important in most clinical trials, they are particularly critical when studying HCC. The cancer staging of HCC must reflect prognosis and, therefore, must include parameters of liver disease. This is because the underlying hepatic dysfunction may often determine how long patients survive and confuse the interpretation of anti-HCC treatment trials. Two new staging paradigms--Cancer of the Liver Italian Program (CLIP) and Chinese University Prognostic Index (CUPI)--have been developed, and these need to be validated. The role of the many different treatment options must be determined. However, the diverse nature of presentation of HCC and the proliferation of many routine procedures--such as chemoembolization or radiofrequency ablation--make controlled trials nearly impossible. Even drug development is a special circumstance, because HCC patients with underlying liver disease may need different dosing regimens and schedules compared to other cancer patients. This makes clinical trial design more cumbersome and the risks of participating in clinical trials for HCC greater. The immense unique challenges of this disease make it imperative for investigators to identify the most promising agents for HCC. At the same time, all patients with HCC should, if possible, be treated on well-designed clinical trials.

Carcinoma, Hepatocellular↗
PubMed2004

Efficacy and safety of liposomal anthracyclines in phase I/II clinical trials.

Preclinical studies have established the pharmacologic advantages of liposomal anthracyclines, including pharmacokinetic profiles after bolus dosing that resemble continuous infusion of conventional anthracyclines, increased drug concentrations in tumor cells compared with the surrounding tissues, and reduced toxicity relative to conventional anthracycline treatment. Based on these studies, many phase I and phase II clinical trials were conducted to assess the safety and potential activity of liposomal anthracyclines in the management of both solid and hematologic tumors. These studies provided valuable insight into the safety of pegylated liposomal doxorubicin (Doxil/Caelyx [PLD]), nonpegylated liposomal doxorubicin (Myocet [NPLD]), and liposomal daunorubicin (DaunoXome [DNX]) over a range of doses, either as single-agent therapy or in combination with other cytotoxic agents. Other liposomal anthracyclines in development may be well tolerated but their activity remains to be elucidated by clinical trials. The available data also suggest that liposomal anthracyclines have activity not only against tumor types with known sensitivity to conventional anthracyclines, but also potentially for tumors that are typically anthracycline-resistant. Despite the availability of clinical data from a wide variety of tumor types and patient populations, further studies of liposomal anthracycline therapy are needed to fully establish their safety, efficacy, and dosing in the treatment of these patients.

Antibiotics, Antineoplastic↗
PubMed2004

Hepatocellular carcinoma: regional therapy with a magnetic targeted carrier bound to doxorubicin in a dual MR imaging/ conventional angiography suite--initial experience with four patients.

Four patients with inoperable hepatocellular carcinoma were treated with a magnetic targeted carrier bound to doxorubicin (MTC-DOX) by using a joint magnetic resonance (MR) imaging/conventional angiography system consisting of a 1.5-T short-bore magnet connected to a C-arm angiography unit by a sliding tabletop. Selective transcatheter delivery of the MTC-DOX to the hepatic artery was monitored by using intraprocedural MR imaging, and interim catheter manipulation was performed with fluoroscopic guidance to optimize agent delivery to the tumor and minimize delivery to normal tissue. The final fraction of treated tumor volume ranged from 0.64 to 0.91. The fraction of affected normal liver volume ranged from 0.07 to 0.30. The dual MR imaging/conventional angiography system shows promise for directing magnetically targeted tumor therapies.

Adult↗