Use of patient-reported outcomes (PRO) data to complement exposure-response analysis in early clinical cancer drug development

BACKGROUND

This proof-of-concept retrospective case study investigated whether patient-reported outcomes (PRO) instruments, designed to capture symptomatic adverse event data, could identity a known exposure-response (ER) relationship for safety characterized in an original FDA analysis of an approved anti-cancer agent. PRO instruments have been designed to uniquely quantify the tolerability aspects of exposure-associated symptomatic adverse events. We explored whether standard ER analyses of clinician-reported safety data for symptomatic adverse events could be complemented by ER analysis using PRO data that capture and quantify the tolerability aspects of these same symptomatic adverse events.

METHODS

Exposure-associated adverse event data for diarrhea were analyzed in parallel in 120 patients enrolled in a clinical trial using physician reported Common Terminology Criteria for Adverse Events (CTCAE) and patient-reported symptomatic adverse event data captured by the National Cancer Institute's (NCI) PRO Common Terminology Criteria for Adverse Events (PRO-CTCAE) instrument. Comparative ER analyses of diarrhea were conducted using the same dataset. Results from the CTCAE and PRO-CTCAE ER analyses were assessed for consistency with the ER relationship for diarrhea established in the original NDA using a 750-patient dataset. The analysis was limited to the 120-patient subset with parallel CTCAE and PRO-CTCAE assessments.

RESULTS

Within the same 120-patient dataset, ER analysis using dense, longitudinal PRO-CTCAE-derived data was sensitive to identify the known ER relationship for diarrhea, whereas the standard CTCAE based ER analysis was not.

CONCLUSIONS

ER analysis using PRO assessed symptomatic adverse event data may be a sensitive tool to complement traditional ER analysis. Improved identification of relationships for safety, by including quantification of the tolerability aspect of symptomatic adverse events using PRO instruments, may be useful to improve the sensitivity of exposure response analysis to support early clinical trial dosage optimization strategies, where decision making occurs within limited small patient datasets.

Land O'Lakes Workshop on Microsampling: Enabling Broader Adoption

The microsampling workshop generated recommendations pertaining to blood sampling site (venous blood versus capillary blood), when to conduct a bridging study, statistical approaches to establish correlation/concordance and deciding on sample size, opportunities and challenges with patient-centric sampling, and how microsampling technology can enrich clinical drug development. Overall, the goal was to provide clarity and recommendations and enable the broader adoption of microsampling supporting patients’ needs, convenience, and the transformation from clinic-centric to patient-centric drug development. The need and adoption of away-from-clinic sampling techniques has become critical to maintain patient safety during the current COVID-19 pandemic.

Abstract 587: Improvement in renal function in patients with multiple myeloma and impaired renal function receiving novel agent induction therapies

BACKGROUND: Renal impairment (RI) is a common complication in patients with multiple myeloma (MM). Effective myeloma treatment can lead to reduction in urinary light-chain excretion and reversibility of RI. Our pooled analysis assessed the magnitude of improvement in renal function (RF) in patients with newly diagnosed (ND) or relapsed and/or refractory (RR) MM treated with novel agent induction therapies, including 3 immunomodulators, 3 proteasome inhibitors, 1 histone deacetylase inhibitor, 1 XP01 inhibitor and 2 monoclonal antibodies.

METHODS: Seventeen registrational trials with 34 treatment arms that collected time profiles of RF during treatment with novel agent induction therapies in 3569 patients with NDMM and 7786 patients with RRMM at baseline were identified from various new drug applications submitted to the US FDA. Change in estimated glomerular filtration rate (eGFR, as estimated by Modification of Diet in Renal Disease formula) compared to baseline was summarized for each therapy.

RESULTS: Increase in eGFR was observed in patients with MM and each category of RI (mild [eGFR 60 - <90 mL/min/1.73 m2], moderate [eGFR 30 - <60 mL/min/1.73 m2] or severe [eGFR 15 - <30 mL/min/1.73 m2]) at baseline who received induction therapies. The time to greatest improvement in eGFR was approximately 3 to 6 months post-treatment. The average improvement in eGFR between Month 3 and 6 post-treatment, as compared to baseline, is summarized in Table 1 for each therapy. Further analysis showed that patients with clinical objective responses (partial response or better) tended to have greater improvement in eGFR than non-responders, especially in patients with NDMM.

Table 1:Improvement in eGFR in patients with MM and RI during the treatment of novel agent induction therapies between Month 3 and 6 as compared to baseline.PatientsTherapyMean (SD) increase in eGFR (mL/min/1.73 m2)% of patients with improvement in eGFR by at least 1 categoryRRMM (N=7786)Monotherapy A8.8 (15.3)33%Monotherapy B-1.5 (10.4)10%Monotherapy C5.9 (13.9)25%Combination D7.7 (15.4)30%Combination E8.9 (17.2)30%Combination F8.1 (14.9)33%Combination G7.6 (14.6)28%Combination H9.5 (16.1)34%Combination I6.5 (14.0)28%Combination J7.4 (14.6)27%Combination K7.6 (14.8)28%Combination L6.4 (12.0)17%Combination M3.1 (14.5)13%Combination N11.2 (17.1)38%NDMM (N-3569)Combination D7.8 (16.4)32%Combination J7.6 (16.0)29%Combination O6.0 (15.2)28%Combination P10.1 (16.7)38%Combination Q10.4 (17.5)37%Combination R11.5 (17.7)38%

CONCLUSIONS: During the treatment with novel agent induction therapies for MM, frequent assessment of RF is needed in patients with RI to guide the proper dosing regimen.

Citation Format: Liang Li, Shuai Hu, Hao Zhu, Yaning Wang, Lian Ma, Brian P. Booth, Nam Atiqur Rahman, Janice Schwartz, Gideon Blumenthal, Qi Liu. Improvement in renal function in patients with multiple myeloma and impaired renal function receiving novel agent induction therapies [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 587.

Current Perspectives on Ligand-Binding Assay Practices in the Quantification of Circulating Therapeutic Proteins for Biosimilar Biological Product Development

Bioanalysis in biosimilar biological product development (BPD) plays a critical role in demonstrating pharmacokinetic (PK) similarity across products. The 2018 FDA Bioanalytical Method Validation guidance for industry provides general principles in the development, validation, and conduct of bioanalytical assays. Given that the PK similarity assessment in BPD programs involves two or more non-identical products, there are additional considerations for bioanalytical methods. Here in, we provide our perspectives on the definition of (1) a single bioanalytical method in the context of BPD in supporting a PK similarity study, (2) bioanalytical method comparability during accuracy and precision experiments to determine the potential bias difference prior to assessing other validation parameters, and (3) bioanalytical method validations that support PK similarity assessments.

Model-informed drug development approach supporting approval of the 4-week (Q4W) dosing schedule for nivolumab (Opdivo) across multiple indications: a regulatory perspective

BACKGROUND

A nivolumab dosage regimen of 480 mg intravenously (i.v.) every 4 weeks (Q4W) was approved by FDA for the majority of the approved indications for nivolumab.

METHODS

The proposed new dosage regimen was supported by pharmacokinetic modeling and simulation, dose/exposure-response relationships for efficacy and safety in the indicated patient populations, and the clinical safety data with the 480 mg Q4W dosage regimen. Pharmacokinetic exposures achieved with 480 mg Q4W were predicted for 4166 patients in 21 clinical studies with various types of solid and hematological tumors. Exposure-response analyses were conducted to predict 480 mg Q4W safety and efficacy across all FDA-approved indications for nivolumab.

RESULTS

For the overall population, the geometric mean exposure achieved with 480 mg i.v. Q4W was 5.2% higher for steady state Cavg and 15.6% lower for Ctrough than those with 3 mg/kg i.v. Q2W, the approved dosage regimen. The simulated concentration-time course achieved with 480 mg Q4W regimen was below the median concentration achieved with 10 mg/kg i.v. Q2W that was also studied in clinical trials. The predicted probability of adverse events was similar between 480 mg Q4W and that observed with the 3 mg/kg Q2W regimen. Efficacy results were found to be similar between Q2W and Q3W dosage regimens in patients with renal cell carcinoma. The predicted efficacy for each indication suggested that the efficacy with 480 mg Q4W is unlikely to be compromised compared with that observed with 3 mg/kg Q2W.

CONCLUSIONS

The model-informed analyses of predicted exposure, efficacy and safety based on data from extensive clinical experience with nivolumab suggest that the benefit-risk profile of 480 mg Q4W regimen is comparable to the approved 3 mg/kg Q2W regimen, thus providing the regulatory basis for the approval of 480 mg Q4W regimen in the absence of clinical efficacy data with this new dosage regimen.

Time dependent pharmacokinetics of pembrolizumab in patients with solid tumor and its correlation with best overall response

Pembrolizumab is a monoclonal antibody that targets the programmed death-1 receptor to induce immune-mediated clearance (CL) of tumor cells. Originally approved by the US Food and Drug Administration in 2014 for treating patients with unresectable or metastatic melanoma, pembrolizumab is now also used to treat patients with non-small-cell lung cancer, classical Hodgkin lymphoma, head and neck cancer, and urothelial cancer. This paper describes the recently identified feature of pembrolizumab pharmacokinetics, the time-dependent or time-varying CL. Overall results indicate that CL decreases over the treatment period of a typical patient in a pattern well described by a sigmoidal function of time with three parameters: the maximum proportion change in CL from baseline (approximately I_max or exactly e^Imax - 1), the time to reach I_max/2 (TI₅₀), and a Hill coefficient. Best overall response per response evaluation criteria in solid tumor category was found to be associated with the magnitude of I_max.

Association of time-varying clearance of nivolumab with disease dynamics and its implications on exposure response analysis

Nivolumab is a human monoclonal antibody that blocks the interaction between PD-1 programmed death-1 (PD-1) and its ligands, PD-L1 and PD-L2. Nivolumab demonstrated efficacy in clinical trials for various types of cancer. A time-varying clearance was identified for nivolumab. We show that the change of clearance over time is associated with the post-treatment effects: clearance decreases when disease status improves. This interaction between posttreatment effects and drug exposure may lead to a biased steep estimate of the exposure-response (E-R) relationship for efficacy. Under this scenario, simulations were performed to develop a proposed methodology to assess the causal effect of drug exposure upon clinical response. Data from nivolumab trials were subsequently used to verify the proposed methodology for E-R analysis. The results showed that E-R analysis results based on pharmacokinetic (PK) metrics derived from the first dose are more consistent with the true E-R or dose-response relationship than the steady-state PK metrics.

Meeting report: metabolites in safety testing (MIST) symposium-safety assessment of human metabolites: what's REALLY necessary to ascertain exposure coverage in safety tests?

In the 2012 AAPS metabolites in safety testing (MIST) symposium held in Chicago, IL, USA, on October 15, 2012, regulatory experts and industrial scientists joined together to discuss their perspectives and strategies in addressing contemporary MIST recommendations (FDA 2008, International Conference on Harmonization (ICH) M3(R2), ICH M(R2) Q&A). Overall, these regulatory guidances indicate that metabolites identified in human plasma should circulate at similar or greater concentrations in at least one of the animal species used in nonclinical safety assessment of the parent drug. However, synthetic standards for the metabolites often do not exist or they are intractable to synthesize, thus introducing multiple challenges in drug development for the quantitative comparison of metabolites between human and animals. A tiered bioanalytical strategy for metabolite analysis is a prevalent approach to demonstrate coverage in animals. Recent developments in bioanalytical methodology have yielded several time- and resource-sparing strategies to provide fit-for-purpose approaches that can enable critical decisions related to metabolite quantification and monitoring in plasma. This report summarizes the presentations and panel discussions at the symposium.

Considerations in Analyzing Single-Trough Concentrations Using Mixed-Effects Modeling

The purpose of this study was to assess the effect of trial design and data analysis choices on the bias and precision of pharmacokinetic (PK) parameter estimation. NONMEM was used to simulate and analyze plasma concentrations collected according to a dense (five samples) or sparse (single-trough samples) sampling scheme for a one-compartment open model with intravenous administration. The results indicated that the bias on estimates of CL with only single-trough data was 17% compared to less than 1% for only dense data. The estimates of CL were improved by fixing all other parameters and estimating only mean and variance of CL (-11% to 1.4%, depending on the estimation method). Adding dense data led to further improvements (-2.3% to 0.3%, depending on further improvements). In these cases, first-order conditional estimation (FOCE) methods resulted in better estimates of CL than first-order (FO) methods. These steps also improved the Bayesian estimates of CL. These studies support the following recommendations: (1) avoid collecting single-trough concentrations unless there is reasonable knowledge about the PK of the drug; (2) if collecting single-trough concentrations is inevitable, avoid estimating all parameters when modeling single-trough concentration data; (3) use prior information by modeling the single-trough concentration data along with dense data from other studies; and (4) use Bayes estimates if the PK model and its parameters are known with reasonable certainty.

The Role of SN-38 Exposure,UGT1A1*28Polymorphism, and Baseline Bilirubin Level in Predicting Severe Irinotecan Toxicity

Irinotecan, an anticancer drug, is associated with severe and potentially fatal diarrhea and neutropenia. The objective of this analysis was to evaluate the role of SN-38 exposure, the active metabolite of irinotecan, UGT1A1 genotypes, and baseline bilirubin on the maximum decrease (nadir) in absolute neutrophil counts following irinotecan. This analysis extended the work of a previous study that examined the effect of UGT1A1 genotypes on the incidence of severe neutropenia in 86 advanced cancer patients following irinotecan treatment. Regression analysis showed that the absolute neutrophil count nadir depended on SN-38 exposure (AUC) and UGT1A1*28 homozygous 7/7 genotype. An increased SN-38 AUC and the 7/7 genotype were significantly associated with a lower absolute neutrophil count nadir (R2 = .49). An alternate model suggested that higher baseline bilirubin and the 7/7 genotype were also significantly associated with a lower absolute neutrophil count nadir, although with a lower coefficient of determination (R2 = .31). Based on these findings and other reports, the irinotecan label was modified to indicate the role of UGT1A1*28 polymorphism in the metabolism of irinotecan and the associated increased risk of severe neutropenia. The label modifications also included recommendations for lower starting doses of irinotecan in patients homozygous for the UGT1A1*28 (7/7) polymorphism.

Assessing proarrhythmic potential of drugs when optimal studies are infeasible

Assessing the potential for a new drug to cause life-threatening arrhythmias is now an integral component of premarketing safety assessment. International Conference on Harmonization of Technical Requirements for Registration of Pharmaceuticals for Human Use Guideline (ICH) E14 recommends the "Thorough QT Study" (TQT) to assess clinical QT risk. Such a study calls for careful evaluation of drug effects on the electrocardiographic QT interval at multiples of therapeutic exposure and with a positive control to confirm assay sensitivity. Yet for some drugs and diseases, elements of the TQT Study may be impractical or unethical. In these instances, alternative approaches to QT risk assessment must be considered. This article presents points to consider for evaluation of QT risk when alternative approaches are needed.

Vorinostat for treatment of cutaneous manifestations of advanced primary cutaneous T-cell lymphoma

PURPOSE

To discuss vorinostat approval for treatment of cutaneous manifestations of advanced cutaneous T-cell lymphoma (CTCL).

EXPERIMENTAL DESIGN

Data from 1 single-arm, open-label, multicenter pivotal trial and 11 other trials submitted to support the new drug application for vorinostat in the treatment of advanced primary CTCL were reviewed. The pivotal trial assessed responses by changes in overall skin disease score using a severity-weighted assessment tool (SWAT). Vorinostat could be considered active in CTCL if observed response rate was at least 20% and the lower bound of the corresponding 95% confidence interval (95% CI) excluded 5%. Patients reported pruritus relief using a questionnaire and a visual analogue scale.

RESULTS

The pivotal trial enrolled 74 patients with stage IB or higher CTCL. Median number of prior treatments was 3, and 61 patients (82%) had stage IIB or higher disease. The objective response rate in the skin disease assessed by change in the overall SWAT score from the baseline was 30% (95% CI, 18.5 to 42.6) in patients with stage IIB or higher disease. Median response duration (end of response defined by 50% increase in SWAT score from the nadir) was 168 days. Median time to tumor progression was 148 days for overall population and 169 days for patients with stage IIB or higher disease. Assessment of pruritus relief was considered unreliable.

CONCLUSIONS

Vorinostat showed activity in CTCL, and skin responses were a clinical benefit. Vorinostat was approved for treatment of cutaneous manifestations of CTCL. A nonblinded, single-arm trial did not allow a reliable assessment of pruritus relief.

Approval summary: sunitinib for the treatment of imatinib refractory or intolerant gastrointestinal stromal tumors and advanced renal cell carcinoma

PURPOSE

To describe the Food and Drug Administration (FDA) review and approval of sunitinib malate (Sutent). Sunitinib received regular approval for the treatment of gastrointestinal stromal tumor (GIST) after disease progression or intolerance to imatinib mesylate (Gleevec). Additionally, sunitinib received accelerated approval for the treatment of advanced renal cell carcinoma.

EXPERIMENTAL DESIGN

For the GIST indication, FDA reviewed data from a randomized, placebo-controlled trial with supportive evidence from a single-arm study. For the advanced renal cell carcinoma indication, FDA reviewed data from two single-arm studies of patients with cytokine-refractory metastatic renal cell carcinoma.

RESULTS

In patients with imatinib refractory or intolerant GIST, time-to-tumor progression of sunitinib-treated patients was superior to that of placebo-treated patients. Median time-to-tumor progression of sunitinib-treated patients was 27.3 weeks, compared with 6.4 weeks for placebo-treated patients (P < 0.0001). Partial responses were observed in 6.8% of sunitinib-treated patients. In patients with metastatic renal cell carcinoma, partial responses were observed in 25.5% (95% confidence interval, 17.5, 34.9) and 36.5% (95% confidence interval, 24.7, 49.6) of patients treated with sunitinib. Median response durations were 27.1 and 54 weeks. The most common adverse events attributed to sunitinib included diarrhea, mucositis, skin abnormalities, and altered taste. Reductions in left ventricular ejection fraction and severe hypertension were also more common in sunitinib-treated patients.

CONCLUSIONS

On January 26, 2006, the FDA approved sunitinib for the treatment of patients with imatinib refractory or intolerant GIST. Accelerated approval was granted for the treatment of advanced renal cell carcinoma.

Population pharmacokinetic-based dosing of intravenous busulfan in pediatric patients

The objective of this study was to characterize the pharmacokinetics (PK) of intravenous busulfan in pediatric patients and provide dosing recommendations. Twenty-four pediatric patients were treated with intravenous busulfan, 1.0 or 0.8 mg/kg for ages < or = 4 years or > 4 years, respectively, 4 times a day for 4 days. Dense PK sampling was performed. Body weight, age, gender, and body surface area were explored for effects on PK, and Monte Carlo simulations were performed to assess different dosing regimens. The PK of intravenous busulfan was described by a 1-compartment model with clearance of 4.04 L/h/20 kg and volume of distribution of 12.8 L/20 kg. Simulations indicated that the mg/kg and mg/m2 regimens were similar and achieved the desired target exposure in approximately 60% of patients. This model suggests that patients < or = 12 kg should be dosed at 1.1 mg/kg and those > 12 kg dosed at 0.8 mg/kg. Therapeutic drug monitoring and dose adjustment will further improve therapeutic targeting.

Approval summary: nelarabine for the treatment of T-cell lymphoblastic leukemia/lymphoma

PURPOSE

To describe the clinical studies, chemistry manufacturing and controls, and clinical pharmacology and toxicology that led to Food and Drug Administration approval of nelarabine (Arranon) for the treatment of T-cell acute lymphoblastic leukemia/lymphoblastic lymphoma.

EXPERIMENTAL DESIGN

Two phase 2 trials, one conducted in pediatric patients and the other in adult patients, were reviewed. The i.v. dose and schedule of nelarabine in the pediatric and adult studies was 650 mg/m2/d daily for 5 days and 1,500 mg/m2 on days 1, 3, and 5, respectively. Treatments were repeated every 21 days. Study end points were the rates of complete response (CR) and CR with incomplete hematologic or bone marrow recovery (CR*).

RESULTS

The pediatric efficacy population consisted of 39 patients who had relapsed or had been refractory to two or more induction regimens. CR to nelarabine treatment was observed in 5 (13%) patients and CR+CR* was observed in 9 (23%) patients. The adult efficacy population consisted of 28 patients. CR to nelarabine treatment was observed in 5 (18%) patients and CR+CR* was observed in 6 (21%) patients. Neurologic toxicity was dose limiting for both pediatric and adult patients. Other severe toxicities included laboratory abnormalities in pediatric patients and gastrointestinal and pulmonary toxicities in adults.

CONCLUSIONS

On October 28, 2005, the Food and Drug Administration granted accelerated approval for nelarabine for treatment of patients with relapsed or refractory T-cell acute lymphoblastic leukemia/lymphoblastic lymphoma after at least two prior regimens. This use is based on the induction of CRs. The applicant will conduct postmarketing clinical trials to show clinical benefit (e.g., survival prolongation).

Impact of pharmacometrics on drug approval and labeling decisions: a survey of 42 new drug applications

The value of quantitative thinking in drug development and regulatory review is increasingly being appreciated. Modeling and simulation of data pertaining to pharmacokinetic, pharmacodynamic, and disease progression is often referred to as the pharmacometrics analyses. The objective of the current report is to assess the role of pharmacometrics at the US Food and Drug Administration (FDA) in making drug approval and labeling decisions. The New Drug Applications (NDAs) submitted between 2000 and 2004 to the Cardio-renal, Oncology, and Neuropharmacology drug products divisions were surveyed. For those NDA reviews that included a pharmacometrics consultation, the clinical pharmacology scientists ranked the impact on the regulatory decision(s). Of about a total of 244 NDAs, 42 included a pharmacometrics component. Review of NDAs involved independent, quantitative evaluation by FDA pharmacometricians, even when such analysis was not conducted by the sponsor. Pharmacometric analyses were pivotal in regulatory decision making in more than half of the 42 NDAs. Of the 14 reviews that were pivotal to approval related decisions, 5 identified the need for additional trials, whereas 6 reduced the burden of conducting additional trials. Collaboration among the FDA clinical pharmacology, medical, and statistical reviewers and effective communication with the sponsors was critical for the impact to occur. The survey and the case studies emphasize the need for early interaction between the FDA and sponsors to plan the development more efficiently by appreciating the regulatory expectations better.

Pemetrexed in malignant pleural mesothelioma

PURPOSE

This report describes the data and analysis leading to the approval of pemetrexed (LY 231514, MTA, Alimta, Eli Lilly and Co., Indianapolis, IN) by the U.S. Food and Drug Administration (FDA) of a New Drug Application for the treatment of malignant pleural mesothelioma (MPM).

EXPERIMENTAL DESIGN

The FDA review of the efficacy and safety of pemetrexed assessed in a randomized clinical trial of 448 patients with unresectable MPM comparing pemetrexed plus cisplatin with cisplatin alone, as well as preclinical pharmacology and chemistry data, are described. The basis for marketing approval is discussed.

RESULTS

In one randomized, single-blind, multicenter international trial, 226 patients were randomized to the pemetrexed and cisplatin arm and 222 patients were randomized to cisplatin alone. Median survival times were 12.1 months for pemetrexed and cisplatin and 9.3 months for cisplatin (P = 0.021; hazard ratio, 0.766; 95% confidence interval, 0.61-0.96). Myelosuppression, predominantly neutropenia, was the most common toxicity of pemetrexed plus cisplatin. Other common adverse events were fatigue, leucopenia, nausea, dyspnea, vomiting, chest pain, anemia, thrombocytopenia, and anorexia.

CONCLUSIONS

Pemetrexed in combination with cisplatin was approved by the FDA on February 4, 2004 for the treatment of patients with MPM whose disease is either unresectable or who are otherwise not candidates for curative surgery. The recommended dose of pemetrexed is 500 mg/m(2) intra venous infusion over 10 minutes on day 1 of each 21-day cycle in combination with 75 mg/m(2) cisplatin infused over 2 hours beginning 30 minutes after the pemetrexed infusion. Patients must receive oral folic acid and vitamin B(12) injections before the start and during therapy to reduce severe toxicities. Patients should also receive corticosteroids with the chemotherapy to decrease the incidence of skin rash. Approval was based on a demonstration of survival improvement in a single randomized trial. Response rates and time to tumor progression were not included in product labeling because of inconsistencies in assessments among the investigators, independent radiologic reviewers, and the FDA, reflecting the difficulty of radiographic assessments in malignant mesothelioma. Complete prescribing information is available on the FDA Web site at http://www.fda.gov/cder/approval/index.htm.

Pemetrexed in Malignant Pleural Mesothelioma

Purpose: This report describes the data and analysis leading to the approval of pemetrexed (LY 231514, MTA, Alimta, Eli Lilly and Co., Indianapolis, IN) by the U.S. Food and Drug Administration (FDA) of a New Drug Application for the treatment of malignant pleural mesothelioma (MPM).

Experimental Design: The FDA review of the efficacy and safety of pemetrexed assessed in a randomized clinical trial of 448 patients with unresectable MPM comparing pemetrexed plus cisplatin with cisplatin alone, as well as preclinical pharmacology and chemistry data, are described. The basis for marketing approval is discussed.

Results: In one randomized, single-blind, multicenter international trial, 226 patients were randomized to the pemetrexed and cisplatin arm and 222 patients were randomized to cisplatin alone. Median survival times were 12.1 months for pemetrexed and cisplatin and 9.3 months for cisplatin (P = 0.021; hazard ratio, 0.766; 95% confidence interval, 0.61-0.96). Myelosuppression, predominantly neutropenia, was the most common toxicity of pemetrexed plus cisplatin. Other common adverse events were fatigue, leucopenia, nausea, dyspnea, vomiting, chest pain, anemia, thrombocytopenia, and anorexia.

Conclusions: Pemetrexed in combination with cisplatin was approved by the FDA on February 4, 2004 for the treatment of patients with MPM whose disease is either unresectable or who are otherwise not candidates for curative surgery. The recommended dose of pemetrexed is 500 mg/m2 intra venous infusion over 10 minutes on day 1 of each 21-day cycle in combination with 75 mg/m2 cisplatin infused over 2 hours beginning 30 minutes after the pemetrexed infusion. Patients must receive oral folic acid and vitamin B12 injections before the start and during therapy to reduce severe toxicities. Patients should also receive corticosteroids with the chemotherapy to decrease the incidence of skin rash. Approval was based on a demonstration of survival improvement in a single randomized trial. Response rates and time to tumor progression were not included in product labeling because of inconsistencies in assessments among the investigators, independent radiologic reviewers, and the FDA, reflecting the difficulty of radiographic assessments in malignant mesothelioma. Complete prescribing information is available on the FDA Web site at http://www.fda.gov/cder/approval/index.htm.

Calcitonin gene-related peptide-dependent vascular relaxation of rat aorta. An additional mechanism for nitroglycerin

We investigated the involvement of calcitonin gene-related peptide (CGRP) in the vasodilatory mechanism of action of nitric oxide (NO) donors. The functional role of CGRP in NO donor-induced vasodilation of isolated rat aortic rings was determined by incubating these drugs with and without CGRP(8-37), a selective CGRP receptor antagonist. CGRP(8-37) (0.63 microM) induced rightward shifts in the vasodilatory concentration-response curves for nitroglycerin (NTG), Piloty's acid (PA), and SIN-1 (linsidomine). The EC(50) values for NTG, PA, and SIN-1 were increased by 8.3-, 5.2-, and 2.3-fold, respectively (P < 0.05). The release of CGRP from rat aorta in response to NTG and PA was measured specifically by radioimmunoassay. Thirty-minute incubations of NTG or PA with rat aorta induced 189.5 and 214.6% increases, respectively, in CGRP release when compared with the control (P < 0.05). The concentration-response curves of sodium nitroprusside (SNP), S-nitroso-acetylpenicillamine (SNAP), tetranitromethane (TNM), diethylamine NO complex (DEA-NO), and diethylenetriamine/nitric oxide adduct (DETA NONOate) were not inhibited significantly by CGRP(8-37) co-incubation (P 0.05). NO donors also were incubated with aortic strips, and NTG and PA alone induced significant formation of hydroxylamine, a NO(-) metabolite (232.4 and 364.9%, respectively, P < 0.05). These results indicate that only NTG and PA, and to a lesser extent SIN-1, stimulate the release of CGRP from the rat aorta, which subsequently contributes to the vasodilatory activity of these agents. The hydroxylamine formation suggests a possible link between NO(-) generation and CGRP release from the vascular wall.

Examination of N-hydroxylation as a prerequisite mechanism of nitric oxide synthase inactivation

L-N5-(1-Hydroxyiminoethyl)-ornithine (L-NHIO) and L-N6-(1-hydroxyiminoethyl)-lysine (L-NHIL) were synthesized and tested as potential intermediates in the mechanism-based inactivation of nitric oxide synthase (NOS) by L-N5-iminoethylornithine (L-NIO) and L-N6-iminoethyllysine (L-NIL). Although these compounds were determined to be competitive inhibitors, mechanism-based inactivation was not observed.

Regulation of in vivo whole blood aggregation in rats by calcitonin gene related peptide

The purpose of these experiments was to determine whether calcitonin gene related peptide (CGRP) mediates physiological control of platelet function in vivo. Rat blood pressure was continuously monitored via a femoral arterial cannula, and whole blood aggregation was assessed periodically ex vivo with an impedance aggregometer before and following a 1.4 nmol/kg bolus dose of CGRP8-37, a specific receptor antagonist of CGRP. Mean arterial blood pressure was not significantly affected by CGRP8-37 over a 30-min period (p > 0.05). However, whole blood aggregation increased by 38.4 ± 18.0% (p < 0.01) and 32.0 ± 11.2% (p < 0.05), at 5 and 15 min post CGRP8-37, respectively, when compared with control. Whole blood aggregation was not significantly different from control at 30 min (p > 0.05), suggesting a relatively short duration of action for in vivo CGRP8-37. These data suggest that CGRP contributes to the maintenance of hemostasis, and that this function may be more important than the better known vasodilatatory effects of this neuropeptide.Key words: hemostasis, calcitonin gene related peptide (CGRP), CGRP8-37, blood pressure, platelet aggregation.

Regulation of in vivo whole blood aggregation in rats by calcitonin gene related peptide

The purpose of these experiments was to determine whether calcitonin gene related peptide (CGRP) mediates physiological control of platelet function in vivo. Rat blood pressure was continuously monitored via a femoral arterial cannula, and whole blood aggregation was assessed periodically ex vivo with an impedance aggregometer before and following a 1.4 nmol/kg bolus dose of CGRP8-37, a specific receptor antagonist of CGRP. Mean arterial blood pressure was not significantly affected by CGRP8-37 over a 30-min period (p>0.05). However, whole blood aggregation increased by 38.4+/-18.0% (p<0.01) and 32.0+/-11.2% (p<0.05), at 5 and 15 min post CGRP8-37, respectively, when compared with control. Whole blood aggregation was not significantly different from control at 30 min (p>0.05), suggesting a relatively short duration of action for in vivo CGRP8-37. These data suggest that CGRP contributes to the maintenance of hemostasis, and that this function may be more important than the better known vasodilatatory effects of this neuropeptide.

Contribution of vascular tissue to the antiplatelet activity of sodium nitroprusside

We tested whether or not platelet inhibition by sodium nitroprusside (SNP) was enhanced by vascular tissue production of nitric oxide (NO) and calcitonin gene-related peptide (CGRP) release. Platelet aggregation was determined with whole blood impedance aggregometry after incubations of SNP in the presence or absence of rat aortic tissue (AT) or AT + CGRPS(8-37) (a specific CGRP antagonist). SNP alone had no effect on platelet aggregation until 100 microM was used (2.3 + 1.5 omega vs. control aggregation of 9.9 +/- 2.0 omega; p < 0.001). Co-incubation of AT with SNP significantly enhanced platelet inhibition at 1 (1.6 +/- 1.3 omega; p < 0.001), 10 (0.7 +/- 0.4 omega; p < 0.001), and 100 microM (0.3 +/- 0.3 omega; p < 0.001). CGRP(8-37) did not significantly antagonize aggregation by SNP + AT (p > 0.05). The inhibition of platelet aggregation by 10 microM SNP was inhibited by methylene blue (MB) (9.0 +/- 1.7 omega at 10 microM; 11.7 +/- 2.4 omega at 100 microM; p < 0.001) but not by 30 microM L-N(upsilon)-monomethyl-L-arginine (L-NMMA; 2.9 +/- 1.8 omega; p > 0.05). These results indicate that vascular tissue significantly contributes to the ability of SNP to inhibit platelet aggregation, probably through greater vascular enzymatic production of NO, but not by releasing CGRP, in contrast to nitroglycerin.

Nitroglycerin-inhibited whole blood aggregation is partially mediated by calcitonin gene-related peptide -- a neurogenic mechanism

1. The role of the vasculature and calcitonin gene-related peptide (CGRP) in nitroglycerin (NTG)-mediated platelet inhibition was studied. 2. In vitro incubations of CGRP in whole blood induced a dose-dependent inhibition of platelet aggregation with an IC50 of 62.1 nM. 3. The platelet inhibition induced by CGRP was blocked by co-incubation of 0.53 microM CGRP8-37, as well as 30 microM N(G)-nitro-monomethyl-L-arginine (L-NMMA). 4. In a separate group of experiments, 100 nM NTG in rat whole blood (WB) induced platelet inhibition of 6.0 +/- 1.3% (mean +/- s.d.), which was enhanced to 77.6+/-3.5% by the addition of rat aortic tissue (AT) (P<0.001). The inclusion of CGRP8-37 with NTG and AT in WB reduced platelet inhibition to 31.6+6.8% (P<0.01). Incubation of WB and AT with 30 microM L-NMMA reduced NTG-induced inhibition of platelet aggregation to 26.4+/-4.2% (P<0.001). 5. It is concluded that vascular tissue contributes to the antiplatelet mechanism of action of NTG. Furthermore, NTG apparently evokes the release of CGRP from vascular tissue and this neuropeptide contributes to the antiplatelet actions of NTG. 6. The antiplatelet activity of CGRP in whole blood is mediated primarily through the activation of nitric oxide synthase.

Sustained antiplatelet properties of nitroglycerin during hemodynamic tolerance in rats

Organic nitrates possess important antiplatelet actions that are useful in the treatment of unstable angina and myocardial infarction, but the susceptibility of platelets to nitrate tolerance has not been extensively studied. In normal conscious rats, we showed that continuous infusion of nitroglycerin (NTG) at 10 micrograms/min had no significant effect on mean arterial pressure (MAP) as compared with control, but hemodynamic tolerance could be demonstrated by MAP response to a bolus intravenous (i.v.) NTG challenge. By this criterion, continuous 8-h NTG infusion produced hemodynamic tolerance (a decrease in MAP response of 45.7 +/- 19.9%, p < 0.05), whereas D5W control and S-nitroso-N-acetylpenicillamine (SNAP) infusions did not. During NTG infusion, platelet-rich plasma (PRP) cyclic GMP was increased by 41.4 +/- 13.6% as compared with control and remained increased throughout the infusion (p < 0.05). Bleeding time during a 2-h infusion of NTG was 8.9 +/- 1.2 min as compared to 3.8 +/- 0.4 min in controls (p < 0.05). After 8-h of NTG infusion, the bleeding time was 10.2 +/- 1.4 min versus 4.4 +/- 0.4 min in controls (p < 0.05). NTG also decreased the PRP platelet concentration by 30% in 8 h, whereas D5W had no effect. In vitro experiments showed that platelets in themselves do not produce significant amounts of cyclic GMP. These data indicate that the biochemical and antiaggregation effects of NTG on platelets are not diminished during hemodynamic tolerance and that these effects may be dependent on extraplatelet production of nitric oxide (NO).

Nitric oxide donors: biochemical pharmacology and therapeutics

The NO donors are a diverse group of agents with unique chemical structures and biochemical requirements for generation of NO. The differences in biochemistry and metabolism may, in turn, cause differences in their pharmacology and therapeutic actions. A thorough understanding of the biochemical pharmacology of NO donors and factors controlling their therapeutic activity would facilitate the optimal use of these agents as chemical carriers of NO, and the development of newer agents than can selectively modulate the many physiological actions of NO.

The effects of hypothermic and normothermic cardiopulmonary bypass on glyceryl trinitrate activity

Glyceryl trinitrate (GTN) is used to control arterial blood pressure during cardiopulmonary bypass (CPB) procedures, but its effects are often decreased during the period of extracorporeal support. The plasma and urine concentrations of GTN and glyceryl-1,2-dinitrate (1,2-GDN) and glyceryl-1,3-dinitrate (1,3-GDN) for male and female patients who received GTN during hypothermic CPB, and male and female patients who were given GTN during normothermic CPB, were measured by gas-liquid chromatography. During hypothermic CPB, the male and female subjects experienced significant decreases in GTN clearance (P < 0.05), 66% and 52%, respectively. Neither the males nor the females who underwent normothermic CPB experienced any significant change in GTN clearance. These results suggest that the lower core temperature during hypothermic CPB may decrease the biotransformation of GTN to GDNs and nitric oxide, thereby resulting in less dilation of blood vessels. Furthermore, the males in the hypothermic CPB group had significantly greater urinary concentrations of 1,3-GDN and 1,2-GDN than the females (P < 0.05), and the normothermic CPB males had a significantly greater urinary concentration of 1,2-GDN than the females in that group. The normothermic CPB males also had significantly higher plasma concentration of GTN at two time points, and 1,3-GDN at one time point, than the females. These data suggest that there may be a gender difference in GTN biotransformation.

Effect of temperature on glyceryl trinitrate induced relaxation of rabbit aorta

It has previously been shown that the vasodilatory response to glyceryl trinitrate (GTN) was decreased during hypothermic cardiopulmonary bypass. The purpose of these experiments was to determine the effect of temperature on GTN-induced relaxation and on GTN biotransformation in rabbit aorta. It was determined that the EC50 of GTN on rabbit aortic rings (RARs) was increased significantly from 1.8 x 10(-8) M at 37 degrees C to 3.4 x 10(-8) M at 27 degrees C (p < 0.05). The production of NO by rabbit aortic strips (RASs) was significantly less at 27 degrees C compared with 37 degrees C after 80 min, being 9.62 x 10(-11) +/- 13.2 x 10(-11) mol NO/g wet wt. RASs compared with 5.71 x 10(-10) +/- 9.43 x 10(-11) mol NO/g wet wt. RASs, respectively (p < 0.05), after 80 min incubation. There was no difference in the amount of glyceryl-1,2-dinitrate (1,2-GDN) produced from GTN at the two temperatures. The ED20 for NO-induced relaxation of RARs increased from 3.46 x 10(-10) +/- 2.24 x 10(-10) mol at 37 degrees C to 1.01 x 10(-9) +/- 4.51 x 10(-10) mol at 27 degrees C (p < 0.05). These data indicate that the biotransformation of GTN and the release of NO were impaired by hypothermia, and that this, as well as a decrease in the tissue response to NO at 27 degrees C, explains the decrease in GTN activity at reduced body temperatures.

Interaction of glyceryl trinitrate and sodium nitroprusside with bovine pulmonary vein homogenate and 10,000 x g supernatant: biotransformation and nitric oxide formation

The current proposed mechanism of action of nitrovasodilator drugs involves biotransformation to nitric oxide, which is postulated to be the active vasodilator substance. Our objective was to determine whether nitric oxide was formed from two prototype nitrovasodilator drugs, glyceryl trinitrate (GTN) and sodium nitroprusside (SNP), after incubation with bovine pulmonary vein (BPV) preparations. GTN or SNP was incubated in an argon atmosphere with phosphate buffer, BPV homogenate, or the 10,000 x g supernatant fraction of the homogenate. Nitric oxide formation, as determined by a chemiluminescence-headspace gas method, was measurable following the incubation of SNP with BPV homogenate and 10,000 x g supernatant. There was no detectable formation of nitric oxide from the incubation of GTN with the two BPV preparations, although GTN was biotransformed to glyceryl dinitrate, as determined by gas-liquid chromatography. There was decreased recovery of nitric oxide during the incubation of authentic nitric oxide with the two BPV preparations as compared with buffer. In conclusion, formation of nitric oxide was measured for the interaction of SNP, but not GTN, with BPV preparations. However, the data do not exclude the possible formation of nitric oxide from GTN, as nitric oxide was shown to be sequestered or transformed by the BPV preparations.

Sequestration of glyceryl trinitrate (nitroglycerin) by cardiopulmonary bypass oxygenators

The effectiveness of glyceryl trinitrate (nitroglycerin) in controlling myocardial ischemia and blood pressure during coronary artery bypass graft surgery is frequently lost during surgery, possibly as a result of drug sequestration by the cardiopulmonary bypass circuit. The objective of this study was to utilize a gas-liquid chromatographic assay to determine the extent of removal of glyceryl trinitrate from the priming fluid by the bubble and membrane oxygenators. The apparatus was maintained at either 25 or 37 degrees C, the two extreme temperatures experienced by the patient during bypass surgery. At apparent steady state, the circulating glyceryl trinitrate concentration was decreased by 20.6%, 46.6%, and 67.3% with the Maxima membrane oxygenator, Cobe membrane oxygenator, and Bentley bubble oxygenator, respectively. The three-layer defoaming filters that are used in the Bentley bubble oxygenator were studied by immersing each of the three filters in fluid containing 60 nM glyceryl trinitrate and monitoring the drug concentration in Plasmalyte. The filters sequestered approximately 90% of the glyceryl trinitrate from the bathing solution of which 31% was recovered with a single methanol wash of the polyurethane filter. These data demonstrate that the different oxygenators used in the cardiopulmonary bypass circuit remove glyceryl trinitrate to varying degrees from the circulating fluid.

Assay of glyceryl trinitrate, isosorbide dinitrate, and their metabolites in plasma by large-bore capillary column gas-liquid chromatography

Two large-bore capillary columns, one with dimethyl polysiloxane (HP-1) as the stationary phase and the other with phenyl (50 per cent) methyl (50 per cent) polysiloxane (DB-17), were used to develop gas-liquid chromatographic (GLC) assays for measuring isosorbide dinitrate (ISDN), glyceryl trinitrate (GTN), and their metabolites. ISDN, isosorbide-2-mononitrate (2-ISMN), and isosorbide-5-mononitrate (5-ISMN) in plasma, ranging in concentration from 1 to 300 nM, and GTN, glyceryl-1,2-dinitrate (1,2-GDN), and glyceryl-1,3-dinitrate (1,3-GDN), ranging in concentration from 3 to 60 nM in plasma, were analysed on both columns. GLC analysis yielded baseline resolution of the analytes. The method using the dimethyl polysiloxane column gave a lower limit of detectability for GTN of 0.75 nM (signal/noise (s/n) = 2), and the procedure using the phenyl-methyl column provided a lower limit of detectability for ISDN of 81 pM (s/n = 2). The large-bore column GLC procedures exhibited shorter retention times for both ISDN and GTN than those previously reported for capillary-column assays. The chromatographic resolution of analytes and column efficiency of the large-bore capillary columns were comparable to the results previously found using capillary-column GC. The assays for ISDN and GTN have been shown to be appropriate for pharmacokinetic studies in volunteers and patients. We determined that the HP-1 column is appropriate for the analysis of GTN and metabolites, and the DB-17 column is suitable for analysis of ISDN and its metabolites. We conclude that the use of large-bore capillary columns provides rapid and reliable GLC assays for organic nitrates.