The MS-275 oral formulation on the daily schedule was intolerable at a dose and schedule explored. The q14-day schedule is reasonably well tolerated. Histone deacetylase inhibition was observed in peripheral-blood mononuclear-cells. Based on PK data from the q14-day schedule, a more frequent dosing schedule, weekly x 4, repeated every 6 weeks is presently being evaluated.

The MTD of infusional flavopiridol is 50 mg/m2/d x 3 with dose-limiting secretory diarrhea at 62.5 mg/m2/d x 3. With ADP, 78 mg/m2/d x 3 was the MTD, with dose-limiting hypotension at 98 mg/m2/d x 3. Based on chronic tolerability, 50 mg/m2/d x 3 is the recommended phase II dose without ADP. Antitumor effect was observed in certain patients with renal, prostate, and colon cancer, and non-Hodgkin's lymphoma. Concentrations of flavopiridol (200 to 400 nM) needed for cyclin-dependent kinase inhibition in preclinical models were achieved safely.

UCN-01 can be administered safely as an initial 72-hour CIV with subsequent monthly doses administered as 36-hour infusions.

Background. The growth‐inhibiting and differentiating effects of sodium phenylacetate against hematopoietic and solid tumor cell lines has aroused clinical interest in its use as an anticancer drug. In an earlier Phase I trial of phenylacetate aimed at maintaining serum drug concentrations in the range that proved active in vitro (>250 μg/ml) for 2 consecutive weeks, infusion rates approached the maximum velocity of drug elimination and commonly resulted in drug accumulation and reversible dose‐limiting neurologic toxicity. In this study, the authors described the nonlinear pharmacokinetics, metabolism, toxicity, and clinical activity of phenylacetate. Methods. The treatment regimen of this Phase I study was designed to expose patients intermittently to drug concentrations exceeding 250 μg/ml and to allow time for drug elimination to occur between doses to minimize accumulation. Sodium phenylacetate was administered as a 1‐hour infusion twice daily (8 a.m., 5 p.m.) at two dose levels of 125 and 150 mg/kg for a 2‐week period. Therapy was repeated at 4‐week intervals for patients who did not experience dose‐limiting toxicity or disease progression. Results. Eighteen patients (4 of whom previously were treated with phenylacetate by continuous intravenous infusion) received 27 cycles of therapy. Detailed pharmacokinetic studies for eight patients indicated that phenylacetate induced its own clearance by a factor of 27% in a 2‐week period. Dose‐limiting toxicity, consisting of reversible central nervous system depression, was observed for three patients at the second dose level. One patient with refractory malignant glioma had a partial response, and one with hormone‐independent prostate cancer achieved a 50% decline in prostate specific antigen level, which was maintained for 1 month. Conclusions. Phenylacetate administered at a dose of 125 mg/kg twice daily for 2 consecutive weeks is well tolerated. High grade gliomas and advanced prostate cancer are reasonable targets for Phase II clinical trials. Cancer 1995;75:2932–8.

The recommended phase II doses of flavopiridol as a 1-hour infusion are 37.5 mg/m(2)/d for 5 days, 50 mg/m(2)/d for 3 days, and 62.5 mg/m(2)/d for 1 day. Flavopiridol as a daily 1-hour infusion can be safely administered and can achieve concentrations in the micromolar range, sufficient to inhibit cyclin-dependent kinases in preclinical models. Further studies to determine the optimal schedule of flavopiridol as a single agent and in combination with chemotherapeutic agents are underway.

No abstract

UCN-01 (7-hydroxystaurosporine; NSC 638850) is a protein kinase antagonist selected for clinical trial based in part on evidence of efficacy in a preclinical renal carcinoma xenograft model. Schedule studies and in vitro studies suggested that a 72-h continuous infusion would be appropriate. In rats and dogs, maximum tolerated doses produced peak plasma concentrations of approximately 0.2-0.3 microM. However, concentrations 10-fold greater are well tolerated in humans, and the compound has a markedly prolonged T1/2. Specific binding to human alpha1-acidic glycoprotein has been demonstrated. These findings reinforce the need to consider actual clinical pharmacology data in "real time" with phase I studies.

IgG-RFB4-SMPT-dgA consists of deglycosylated ricin A chain (dgA) coupled to the monoclonal antihuman CD22 antibody, RFB4. This study determined the maximally tolerated dose (MTD) of this immunotoxin (IT) administered as a continuous 8-day infusion to 18 patients with B-cell lymphoma (30% CD22+ tumor cells) over 8 days. The MTD was 19.2 mg/m2/192 h (maximum toxicity grade 1), with vascular leak syndrome (VLS) as dose-limiting toxicity (DLT) at 28.8 mg/m2/192 h (grades 3 through 5 in 7 of 11 patients). Predictors of severe VLS included serum IT concentrations greater than 1,000 ng/mL and the absence of circulating tumor cells. Decreased urine sodium excreted in 24 hours provided evidence for mild VLS without notable changes in serum albumin. Four partial responses, 3 minor responses, 6 stable disease, and 3 progression of disease were observed. The mean maximal serum concentration (Cmax) in initial courses at the MTD (19.2 mg/m2) was 443 +/- 144 ng/mL (n = 3; range, 326 to 604). At 28.8 mg/m2/192 h, the Cmax was highly variable (n = 11; mean, 1,102 +/- 702; range, 9.6 to 2,032 ng/mL). Human antimouse or antiricin antibodies developed in 6 of 16 (37.5%) patients after one course of IT. However, 10 eligible patients received multiple courses of IT. Changes in serum cytokines and cytokine receptors did not correlate with toxicity but decreased soluble interleukin-2 receptor concentrations correlated with clinical response. Comparison to a prior study with the same IT administered by intermittent bolus infusions (Amlot et al, Blood 82:2624, 1993) suggests similar clinical response, toxicity, and immunogenicity.