James M. Pluda

Clinical Trial Designs for Cytostatic Agents: Are New Approaches Needed?

Preclinical data suggest that some new anticancer agents directed at novel targets demonstrate tumor growth inhibition but not tumor shrinkage. Such cytostatic agents may offer clinical benefits for patients in the absence of tumor shrinkage. In addition, lower doses of some of these agents may be just as effective as higher doses, implying that toxicity may not be an ideal end point for dose finding. Because of these factors, the sequence and design of traditional phase I, II, and III trials used for cytotoxic agents (which typically shrink tumors and in a dose-dependent manner) may not be appropriate for cytostatic agents. This article discusses options for modifying trial designs to accommodate cytostatic agents. Examples are given where these options have been tried or are currently being tried. Recommendations given for choosing among the trial designs depend on what is known preclinically about the agents (eg, does one have a validated and reproducible biologic end point that can be used to guide a dose escalation?), what is known about the patient population being studied (eg, does one have a well-documented historical progression-free survival rate at 1 year for comparison with the experience of the new agent?), and the numbers of agents and patients available for participation in trials. Planned and ongoing trials will test the utility of some of these new approaches.

Activity of Thalidomide in AIDS-Related Kaposi’s Sarcoma

PURPOSE To assess the toxicity and activity of oral thalidomide in Kaposis sarcoma (KS) in a phase II dose-escalation study. PATIENTS AND METHODS Human immunodeficiency virus (HIV)-seropositive patients with biopsy-confirmed KS that progressed over the 2 months before enrollment received an initial dose of 200 mg/d of oral thalidomide in a phase II study. The dose was increased to a maximum of 1,000 mg/d for up to 1 year. Anti-HIV therapy was maintained during the study period. Toxicity, tumor response, immunologic and angiogenic factors, and virologic parameters were assessed. RESULTS Twenty patients aged 29 to 49 years with a median CD4 count of 246 cells/mm(3) (range, 14 to 646 cells/mm(3)) were enrolled. All patients were assessable for toxicity, and 17 for response. Drowsiness in nine and depression in seven patients were the most frequent toxicities observed. Eight (47%; 95% confidence interval [CI], 23% to 72%) of the 17 assessable patients achieved a partial response, and an additional two patients had stable disease. Based on all 20 patients treated, the response rate was 40% (95% CI, 19% to 64%). The median thalidomide dose at the time of response was 500 mg/d (range, 400 to 1,000 mg/d). The median duration of drug treatment was 6.3 months, and the median time to progression was 7.3 months. CONCLUSION Oral thalidomide was tolerated in this population at doses up to 1,000 mg/d for as long as 12 months and was found to induce clinically meaningful anti-KS responses in a sizable subset of the patients. Additional studies of this agent in KS are warranted.

A randomized phase II trial of docetaxel (taxotere) plus thalidomide in androgen-independent prostate cancer.

New therapeutic alternatives are needed to improve outcomes in patients with androgen-independent prostate cancer (AIPC). For several years, researchers at the National Cancer Institute have been interested in elucidating the importance of angiogenesis in the pathogenesis of prostate cancer and in identifying inhibitors of this process. Thalidomide has been shown to inhibit the ability of tumors to recruit new blood vessels. In a recent phase II trial of thalidomide in AIPC, 28% of patients achieved a prostate-specific antigen (PSA) decrease of >40%. The taxane docetaxel also produces PSA and measurable disease responses when used as monotherapy or as a component of combination chemotherapy for AIPC. Thus, based on the single-agent activity of thalidomide and docetaxel, we initiated a randomized phase II study of weekly docetaxel with or without thalidomide, 200 mg at bedtime, in patients with chemotherapy-naive metastatic AIPC. Docetaxel, 30 mg/m(2) intravenously, was administered every 7 days for 3 weeks, followed by a 1-week rest period. Both regimens have been well tolerated among the first 59 treated patients, with a near absence of grade (3/4) myelosuppression. Fatigue, hyperglycemia, and pulmonary toxicity were seen in both groups. Thrombotic events have been seen in the combination arm. Thirty-five percent (6 of 17) of the patients receiving docetaxel alone and 53% (19 of 36) of those receiving docetaxel and thalidomide have had a PSA decrease of at least 50%. Combining a cytotoxic agent with an angiogenesis inhibitor is a promising area of investigation for prostate cancer management.

Phase II Evaluation of Thalidomide in Patients With Metastatic Breast Cancer

PURPOSE To determine the efficacy, safety, pharmacokinetics, and effect on serum angiogenic growth factors of two dose levels of thalidomide in patients with metastatic breast cancer. PATIENTS AND METHODS Twenty-eight patients with progressive metastatic breast cancer were randomized to receive either daily 200 mg of thalidomide or 800 mg to be escalated to 1,200 mg. Fourteen heavily pretreated patients were assigned to each dose level. Each cycle consisted of 8 weeks of treatment. Pharmacokinetics and growth factor serum levels were evaluated. RESULTS No patient had a true partial or complete response. On the 800-mg arm, 13 patients had progressive disease at or before 8 weeks of treatment and one refused to continue treatment. The dose was reduced because of somnolence to 600 mg for five patients and to 400 mg for two and was increased for one to 1,000 mg and for four to 1,200 mg. On the 200-mg arm, 12 patients had progressive disease at or before 8 weeks and two had stable disease at 8 weeks, of whom one was removed from study at week 11 because of grade 3 neuropathy and the other had progressive disease at week 16. Dose-limiting toxicities included somnolence and neuropathy. Adverse events that did not require dose or schedule modifications included constipation, fatigue, dry mouth, dizziness, nausea, anorexia, arrhythmia, headaches, skin rash, hypotension, and neutropenia. Evaluation of circulating angiogenic factors and pharmacokinetic studies failed to provide insight into the reason for the lack of efficacy. CONCLUSION Single-agent thalidomide has little or no activity in patients with heavily pretreated breast cancer. Further studies that include different patient populations and/or combinations with other agents might be performed at the lower dose levels.

A Pilot Study of Cidofovir in Patients with Kaposi Sarcoma

A clinical trial was conducted to test the activity of cidofovir (CDV), a drug with in vitro activity against Kaposi sarcoma (KS)-associated herpesvirus (KSHV), in KS. Five patients with human immunodeficiency virus-associated KS (4 receiving antiretroviral therapy) and 2 patients with classical KS were administered CDV (5 mg/kg/dose) weekly for 2 weeks and then every other week. All 7 patients had progression of their KS at a median of 8.1 weeks (range, 5-27 weeks). Skin biopsy specimens of KS lesions showed no change in expression of latent or early lytic genes, but, in the 1 assessable patient, there was decreased expression of a late lytic gene. There was no decrease in the virus load of KSHV in peripheral blood mononuclear cells. This study does not provide proof of principle for the treatment of KS with CDV. However, it remains possible that antiherpesvirus therapy can be developed for herpes-induced tumors.

Approaches to preclinical screening of antiangiogenic agents

Angiogenesis, or new blood vessel growth, is essential for the growth, invasion, and metastasis of solid tumors. The inhibition of this process, or antiangiogenesis, is a promising new therapeutic anticancer strategy. Several antiangiogenic compounds are currently in preclinical or clinical development for the treatment of cancer. However, the challenge for the discovery and characterization of antiangiogenic targets remains in developing efficient in vitro or in vivo preclinical angiogenesis screening assays to assess and compare antiangiogenic activity. Several semiquantitative or quantitative angiogenesis assays exist, including in vitro endothelial cell systems and ex vivo or in vivo neovascularization models utilizing mouse, rat, or human tissues. We describe the more common and cost-effective angiogenesis assays currently in use, summarizing their unique advantages and disadvantages. Since angiogenesis inhibition is a novel therapeutic modality towards controlling solid tumors, antiangiogenic drug development underlines the importance in describing, standardizing, and developing quantitative screening assays for the next generation of antiangiogenic agents.

Clinical Trial Designs for Cytostatic Agents

To the Editor: We read with great interest the special article on clinical trial designs for cytostatic agents written by Cancer Therapy Evaluation Program (CTEP) investigators, 1 having recently authored a similar article ourselves. 2 It is widely recognized that the historical approach to oncology drug development cannot be explicitly used for putative cytostatic agents. This is particularly applicable to phase II trials, where the historical approach of using small cohorts to look for a minimum response rate will clearly fail for drugs for which a classical partial response is not anticipated. 3 Korn et al suggest that progression-free survival in a 30to 50-patient cohort can be compared with that of historical controls. In our opinion, this approach is unlikely to be of benefit because of selection bias, lack of standardized data collection in many historical series, as well as the recent change in criteria for response and progression developed in part by CTEP investigators. 4

CLINICAL TRIAL DESIGNS FOR CYTOSTATIC AGENTS AND AGENTS DIRECTED AT NOVEL MOLECULAR TARGETS

Publisher Summary This chapter discusses clinical trial designs for cytostatic agents and agents directed at novel molecular targets. The usual clinical development of chemotherapeutic agents proceeds through three phases of human testing. Phase I trials are designed to find the dose to be recommended for further testing by finding the highest dose that has acceptable toxicity. Some cytostatic agents and agents directed at novel molecular targets have properties that raise questions about whether this standard developmental pathway is appropriate or optimal. It is found that if the goal of a trial is to find the maximum tolerated dose to be used for further testing, then a standard design using cohorts of 3–6 patients treated at escalating dose levels can be used. The chapter explores whether or not it is possible to design a study with enough patients at a dose level to ensure with high probability that after observing the responses one can be 90% confident that the true response rate is greater than some specified level. With only two dose levels, the response at each dose level could be estimated and a statistical hypothesis test to ascertain the statistical significance of the difference in biologic responses performed. It is suggested to perform multi-arm randomized selection design where multiple new agents are compared to each other with the agent showing the best clinical effects chosen to be tested further.

Phase II Evaluation Of Thalidomide In Patients With Metastatic Breast Cancer

Purpose: To determine the efficacy, safety, pharmacokinetics, and effect on serum angiogenic growth factors of two dose levels of thalidomide in patients with metastatic breast cancer. Patients and Methods: Twenty-eight patients with progressive metastatic breast cancer were randomized to receive either daily 200 mg of thalidomide or 800 mg to be escalated to 1,200 mg. Fourteen heavily pretreated patients were assigned to each dose level. Each cycle consisted of 8 weeks of treatment. Pharmacokinetics and growth factor serum levels were evaluated. Results: No patient had a true partial or complete response. On the 800-mg arm, 13 patients had progressive disease at or before 8 weeks of treatment and one refused to continue treatment. The dose was reduced because of somnolence to 600 mg for five patients and to 400 mg for two and was increased for one to 1,000 mg and for four to 1,200 mg. On the 200-mg arm, 12 patients had progressive disease at or before 8 weeks and two had stable disease at 8 weeks, of whom one was removed from study at week 11 because of grade 3 neuropathy and the other had progressive disease at week 16. Dose-limiting toxicities included somnolence and neuropathy. Adverse events that did not require dose or schedule modifications included constipation, fatigue, dry mouth, dizziness, nausea, anorexia, arrhythmia, headaches, skin rash, hypotension, and neutropenia. Evaluation of circulating angiogenic factors and pharmacokinetic studies failed to provide insight into the reason for the lack of efficacy. Conclusion: Single-agent thalidomide has little or no activity in patients with heavily pretreated breast cancer. Further studies that include different patient populations and/or combinations with other agents might be performed at the lower dose levels.