Determinants of the sensitivity of human small-cell lung cancer cell lines to methotrexate.

We have characterized the determinants of methotrexate (MTX) responsiveness in eight patient-derived cell lines of small-cell lung cancer (SCLC). Clonogenic survival was correlated with factors known to affect sensitivity to drug. NCI-H209 and NCI-H128 were most drug sensitive, with drug concentrations required to inhibit clonogenic survival by 50% with less than 0.1 microM MTX. Six cell lines (NCI-H187, NCI-H345, NCI-H60, NCI-H524, NCI-H146, and NCI-N417D) were relatively drug resistant. In all cell lines studied, higher molecular weight MTX-polyglutamates (MTX-PGs) with 3-5 glutamyl moieties (MTX-Glu3 through MTX-Glu5) were selectively retained. Relative resistance to low (1.0 microM) drug concentrations appeared to be largely due to decreased intracellular metabolism of MTX. Five of the six resistant lines were able to synthesize polyglutamates at higher (10 microM) drug concentrations, although one resistant cell line (NCI-N417D) did not synthesize higher molecular weight MTX-PGs, even after exposure to 10 microM drug. Two cell lines with resistance to 10 microM MTX (NCI-H146 and NCI-H524) synthesized and retained higher molecular weight MTX-PGs in excess of binding capacity after exposure to 10 microM drug. However, the specific activity of thymidylate synthase in these cell lines was low. MTX sensitivity in patient-derived cell lines of SCLC requires the ability of cells to accumulate and retain intracellular drug in the form of polyglutamate metabolites in excess of dihydrofolate reductase, as well as a high basal level of consumption of reduced folates in the synthesis of thymidylate.

Phase I trial of piritrexim capsules using prolonged, low-dose oral administration for the treatment of advanced malignancies.

A phase I trial of piritrexim was conducted by use of a prolonged, low-dose oral schedule. A number of different regimens were tested, including daily dosing for 21 days followed by 7 days of no drug therapy; continuous dosing; and daily dosing for 5 of 7 days for 3 consecutive weeks followed by a week of rest. Dose escalation was accomplished by increasing the dosing frequency from once a day to twice a day and then to three times a day and by increasing the number of days of administration. Fifty-one patients with advanced cancer were entered in the study. One hundred twenty-four (96%) of 129 courses were considered assessable. Myelosuppression proved to be the dose-limiting toxic effect. Other toxic effects included stomatitis, nausea and vomiting, anorexia, diarrhea, skin rash, fatigue, and elevation of liver transaminase levels. Antitumor activity was observed in patients with melanoma and bladder cancer, and disease stabilization occurred in those with sarcoma and pheochromocytoma. The recommended dosing schedule for phase II clinical trials is 25 mg three times a day for 5 days for 3 consecutive weeks followed by 1 week of no drug therapy.

Pediatric phase I trial, pharmacokinetic study, and limited sampling strategy for piritrexim administered on a low-dose, intermittent schedule.

Piritrexim, an orally administered, lipid-soluble antifolate, was evaluated in a multi-institutional phase I trial in children. The starting dose was 10 mg/m2/dose administered every 8 h daily for 5 days for 3 consecutive weeks, with dose escalations in increments of 5 mg/m2/dose. Eighteen patients (16 with metastatic sarcoma, 1 with acute lymphoblastic leukemia, and 1 with a brainstem glioma), 3.5-20 years of age, with malignancy refractory to therapy, were entered into the study. The dose-limiting toxicities (DLTs), which were myelosuppression and mucositis, occurred in 4 of 4 patients treated at the 25-mg/m2/dose level but in none of the patients treated at the 15- and 20-mg/m2/dose levels. The recommended dose for phase II trials is 20 mg/m2/dose. Pharmacokinetic monitoring was performed in 15 of the 18 children. The area under the concentration-time curve (AUC) was linearly related to the dose administered. Piritrexim was rapidly absorbed, with the median time to peak level occurring 1.5 h after an oral dose. The terminal half-life of piritrexim ranged from 1.5 to 4.5 h. A limited sampling strategy developed earlier, capable of predicting the AUC based on the plasma concentrations at 3 and 6 h after an oral dose, was prospectively tested in this trial and proved to be highly predictive of the AUC (r = 0.98, P = 0.0001). Pharmacodynamic-pharmacokinetic correlations were obtained after combining data from this and the prior phase I pediatric trial. Trough plasma piritrexim concentration strongly correlated with DLT (P = 0.0016). A trough plasma piritrexim concentration greater than 0.5 microM appeared to be predictive of toxicity. Eleven of 15 patients with trough concentrations exceeding this threshold experienced DLTs. Therapeutic drug monitoring may thus play an important role in adjusting the dose and schedule of piritrexim in future trials.

Pediatric phase I trial and pharmacokinetic study of piritrexim administered orally on a five-day schedule.

Piritrexim, a new nonclassical antifolate, was evaluated in a multiinstitutional phase I trial in children. The starting dose was 290 mg/m2/day, administered p.o. every 12 h for 5 consecutive days, with courses repeated every 21 days. Dose reduction, initially to 200 mg/m2/day and subsequently to 140 mg/m2/day, was required because dose limiting myelosuppression and mucositis were encountered at the 290- and 200-mg/m2/day dose levels. Non-dose limiting toxicities included transient elevations in liver function tests, mild nausea, and skin rashes. The maximum tolerated dose was 140 mg/m2/day for 5 days. Pharmacokinetic monitoring was performed at steady state during the first course. For the 140-, 200-, and 290-mg/m2/day dose groups, the mean +/- SE peak plasma concentrations were 5.3 +/- 0.84, 9.3 +/- 1.7, and 10.2 +/- 2.3 microM, respectively, and occurred at a median of 1.5 h following the p.o. dose. The mean area under the plasma concentration-time curves were 18.1 +/- 2.3, 45.4 +/- 8.9, and 56.9 +/- 16.3 microM.h, respectively. Absolute bioavailability in two patients who were also monitored following a single i.v. dose of 140 and 200 mg/m2/day of piritrexim was 35 and 93%, respectively. Dose limiting toxicities were observed in 9 of 10 patients with 12-h trough piritrexim concentrations greater than 0.5 microM, whereas only 2 of 7 patients with trough concentrations less than 0.5 microM experienced dose limiting toxicities. A limited pharmacokinetic sampling strategy that allowed the area under the plasma concentration-time curve to be accurately predicted from the 3- and 6-h plasma drug concentration was developed. The recommended dose for future phase II trials is 140 mg/m2/day administered p.o. every 12 h for 5 consecutive days. Pharmacokinetic monitoring at 3, 6, and 12 h postdose may be useful for estimating bioavailability and for predicting which patients are at greatest risk for developing toxicity.

Phase II trial of piritrexim in metastatic melanoma using intermittent, low-dose administration.

A phase II trial of piritrexim (2,4-diamino-6[2,5-dimethoxybenzyl]-5-methyl pyrido-[2,3d] pyrimidine, 301U74; PTX) was conducted for patients with metastatic malignant melanoma using an intermittent, low-dose oral administration schedule. PTX was administered at a starting dose of 25 mg orally three times per day for 5 days weekly for 3 weeks followed by 1 week of rest. Thirty-one patients were entered onto the study. Among 31 patients assessable for response, there were two complete responses (CRs) and five partial responses (PRs) for a response rate (CR plus PR) of 23% (95% confidence limit, 10% to 42%). Five responses occurred in soft tissue lesions, and two responses occurred in lung lesions. The initial dose schedule was well tolerated. The dose-limiting toxicity was myelosuppression. PTX administered in this schedule appears to be active against malignant melanoma. Further clinical trials to confirm these results are underway.

Preclinical and phase I clinical studies with the nonclassical antifolate thymidylate synthase inhibitor nolatrexed dihydrochloride given by prolonged administration in patients with solid tumors.

PURPOSE: A phase I, multicenter trial of the thymidylate synthase (TS) inhibitor THYMITAQ (nolatrexed dihydrochloride; Agouron Pharmaceuticals, Inc, San Diego, CA) given by 5-day continuous infusion was performed to establish the maximum-tolerated dose (MTD) and to investigate pharmacokinetics, pharmacodynamics, and antitumor effects. METHODS: In vitro and in vivo preclinical studies demonstrated increased activity with prolonged nolatrexed exposure. In 32 patients, nolatrexed was given as a 5-day infusion at 96 to 1,040 mg/m2/d for 5 days. Pharmacokinetics were determined from high-performance liquid chromatography (HPLC) analyses of plasma and urine. In addition to studying toxicity, plasma deoxyuridine (UdR) elevations were measured as a marker of TS inhibition. RESULTS: The MTD was 904 mg/m2/d for 5 days and the recommended phase II dose is 800 mg/m2/d for 5 days. The dose-limiting toxicity was neutropenia with clinically significant thrombocytopenia and mucositis. These antiproliferative toxicities of nolatrexed were predictable and reversible. A partial response that lasted 3 months occurred in a patient with metastatic colorectal cancer. Pharmacokinetics were nonlinear, with the median plasma clearance (CI) decreasing from 151 mL/min/m2 (range, 124 to 211) at 96 mg/m2/d for 5 days to 49 mL/min/m2 (range, 30 to 84) at 768 mg/ m2/d for 5 days. The half-life (t1/2) was 173 minutes (range, 43 to 784) and 18% (range, 9% to 35%) of the dose was excreted unchanged in the urine. Plasma UdR increased, but returned to pretreatment levels after the end of infusion. Hematologic toxicity was significantly related to nolatrexed plasma concentrations and dose. CONCLUSION: Nolatrexed can be safely administered to patients at a dose of 800 mg/m2/d over 5 days by continuous intravenous infusion and this schedule is associated with antitumor effects. The phase II evaluation of nolatrexed is ongoing.

Phase I studies with the nonclassical antifolate nolatrexed dihydrochloride (AG337, THYMITAQ) administered orally for 5 days.

Phase I studies of p.o. administered nolatrexed dihydrochloride (AG337, THYMITAQ), a nonclassical thymidylate synthase inhibitor, were performed to establish the maximum tolerated dose and a recommended dose for Phase II studies. The bioavailability and pharmacokinetic and pharmacodynamic properties of oral nolatrexed were also studied. Forty-five patients were treated with oral nolatrexed every 6 h for 5 days at doses of 288-1000 mg/m2/day. The bioavailability of the oral preparation was determined, and the effect of a standard meal on nolatrexed absorption was investigated at a dose of 800 mg/m2/day. Nolatrexed plasma concentrations were analyzed by high-performance liquid chromatography. Nolatrexed was rapidly absorbed with a median bioavailability of 89% (range 33-116%), with 88% of patients above 70%. The dose-limiting toxicities were gastrointestinal, and the recommended Phase II oral dose was 800 mg/m2/day. After a standard meal, the peak plasma nolatrexed concentration achieved was lower (median, 8.3 microg/ml versus 15.0 microg/ml; P = 0.001), and the time taken to reach the peak was longer (median, 180 min versus 45 min; P = 0.00003), but the trough concentration was higher (median, 3.6 microg/ml versus 2.1 microg/ml; P = 0.004) when compared with the fasted state. The area under the nolatrexed plasma concentration versus time curve was not affected by food. Average trough nolatrexed concentration, but not dose, was significantly related to the % decrease in both thrombocytes (r2 = 0.58; C50 = 6.0 microg/ml, where C50 is the plasma concentration associated with a 50% decrease in thrombocytes) and neutrophils (r2 = 0.63; C50 = 0.6 microg/ml). Nolatrexed can be safely administered as an oral preparation at a dose of 800 mg/m2/day for 5 days. Bioavailability was close to 100% and, because inhibition of thymidylate synthase by nolatrexed is rapidly reversible, the slower absorption after a standard meal may result in a shorter duration of noninhibitory concentrations between doses.

Phase I trial of the thymidylate synthase inhibitor AG331 as a 5-day continuous infusion.

AG331 (N6-[4-(morpholinosulfonyl)benzyl]-N6-methyl-2, 6-diaminobenz-[c,d]-indole glucuronate) is a lipophilic thymidylate synthase inhibitor with activity in solid tumor models. On the basis of preclinical data supporting regimens of frequent drug administration, we performed a Phase I trial of AG331 as a 5-day continuous infusion repeated every 3 weeks. Twenty-nine patients were entered at doses ranging from 25 to 1000 mg/m2/day. The major side effects were mild to moderate fatigue, nausea, vomiting, diarrhea, and fever. At doses >/=400 mg/m2, acute reversible elevation of bilirubin, aspartate aminotransferase, alanine aminotransferase, and gamma-glutamyltranspeptidase was observed. All patients who received >/=600 mg/m2/day experienced elevated alanine aminotransferase. Elevated liver function tests were evident by day 3 of the infusion and had resolved by day 8 in the majority. This toxicity was dose limiting at 1000 mg/m2/day, at which dose two of two patients developed grade 4 reversible hyperbilirubinemia in addition to the enzyme elevations. Serum and urine samples were analyzed by a novel high-pressure liquid chromatography method for the determination of the pharmacokinetics of AG331. Over the 50-1000 mg/m2/day dose range, mean total clearance ranged from 11.6 to 30.0 liters/h/m2, and volume of distribution at steady state ranged from 279.5 to 758.7 liters/m2. These parameters were dose independent over the dose range tested. The harmonic mean terminal half-life of AG331 was 20.2 h. Less than 5% of an AG331 dose is eliminated unchanged in the urine. Both the administered dose and exposure to the drug were related to the changes in bilirubin and aminotransferase blood levels. Evidence for inhibition of thymidylate synthase was obtained at doses ranging from 100 to 1000 mg/m2 in seven patients; plasma deoxyuridine concentrations at end-infusion were 1.8-3.8-fold higher than pretreatment values. Because of the nature of toxicity on this schedule, more extensive Phase II evaluation is not recommended, although an AG331 dose of 800 mg/m2/day for 5 days is tolerable. Exploration of less frequent dose administration is under way.

Predictors of optimal virological response to potent antiretroviral therapy.

BACKGROUND: Current potent antiretroviral therapy (using a protease inhibitor and two nucleoside reverse transcriptase inhibitors) produces a durable suppression of HIV replication in less than 75% of treated patients. Identification of predictors of successful therapy might allow the development of improved strategies to increase response rates. METHODS: We analyzed retrospectively the results from a multicenter, randomized, double-blind Phase III study of combination anti-HIV therapy with nelfinavir, zidovudine, and lamivudine to evaluate the relationship between virological response over 48 weeks of treatment to variables which could potentially serve as early predictors of long-term response. The goal was to produce long-term suppression of viral load to sensitive (<400 copies HIV RNA/ml) and ultrasensitive (<50 copies HIV RNA/ml) limits of quantification with the Amplicor PCR assay. FINDINGS: Baseline viral load, the change in viral load over the first 4 weeks of treatment, the 2 h post-dose nelfinavir levels and the time to respond to HIV RNA levels of <400 copies/ml and <50 copies/ml have the best predictive value in determining response and response duration. Patients who achieved very low viral nadirs (<50 copies HIV RNA/ml) had significantly longer responses than those who achieved nadirs of 50-400 copies HIV RNA/ml. INTERPRETATION: Parameters that can be measured easily at baseline or early after therapy is started can identify patients at high risk of failure with standard treatment. Such patients may be candidates for more aggressive therapy or for alternative strategies designed to improve outcome. In addition, these results support the use of ultra-sensitive HIV RNA assays to predict long-term outcome of anti-HIV therapy.

Randomized, double-blind comparison of two nelfinavir doses plus nucleosides in HIV-infected patients (Agouron study 511).

OBJECTIVE: To evaluate the safety and antiretroviral activity of nelfinavir mesylate at two doses as part of a combination regimen in HIV-infected, antiretroviral-naive patients. DESIGN: Phase III, multicenter, double-blind, placebo-controlled trial. PATIENTS AND METHODS: Two-hundred and ninety-seven patients were randomized to one of three treatment groups: nelfinavir 750 mg three times daily (tid), nelfinavir 500 mg tid, or matching placebo, each in combination with open-label zidovudine (ZDV) 200 mg tid and lamivudine (3TC) 150 mg twice daily (bid). Data were analyzed on an intent-to-treat basis. RESULTS: Sixty-seven percent of patients receiving nelfinavir 750 mg tid, and 50% receiving nelfinavir 500 mg tid in combination with ZDV/3TC achieved HIV RNA < 400 copies/ml compared to 7% receiving ZDV/3TC plus placebo (P < 0.001); 55% and 30% of patients in the nelfinavir-containing arms achieved HIV RNA < 50 copies/ml at week 24. This compared with 4% in the placebo-containing arm. For patients continuing nelfinavir treatment (750 mg or 500 mg tid as treated) for a further 6 months, the proportions achieving < 400 copies/ml at week 48 were 75% and 54% (P = 0.001) and < 50 copies/ml 61% and 37%, respectively (P = 0.004). The mean increases from baseline in CD4 cell counts were also durable in patients receiving the triple combination nelfinavir therapy. The range and incidence of adverse events was similar for the two nelfinavir-containing arms, with diarrhea being the most common adverse event. CONCLUSIONS: Nelfinavir plus ZDV/3TC was superior to ZDV/3TC/placebo. In addition, the 750 mg tid nelfinavir dose was better than the 500 mg tid dose. Virologic responses were sustained over 12 months.

Safety, pharmacokinetics, and antiretroviral activity of the potent, specific human immunodeficiency virus protease inhibitor nelfinavir: results of a phase I/II trial and extended follow-up in patients infected with human immunodeficiency virus.

The safety, antiretroviral activity, and pharmacokinetic profile of nelfinavir, a potent and specific inhibitor of human immunodeficiency virus (HIV) protease, were assessed in a small open-label phase I/II dose-ranging study in protease inhibitor-naive HIV-positive men. A total of 22 patients with baseline plasma HIV RNA > or = 20,000 copies/mL and CD4+ counts between 200 and 500 cells/mm3 were enrolled in the study. Of the 22 patients, 20 were evaluated for activity; 10 patients assigned to 771 mg/day base equivalent (300 mg three times daily) and 10 patients assigned to 1,026 mg/day base equivalent (600 mg twice daily) given monotherapy. A capsule formulation of nelfinavir was used. The initial study period was 28 days; patients showing a virologic response of 1 log10 reduction were eligible for enrollment in an extension phase and addition of nucleoside analogues. A maximally tolerated dose of nelfinavir was not established. A dose-response relationship was observed for four (40%) patients in the 771-mg group and six (60%) patients in the 1,026-mg group experiencing a reduction from baseline in plasma HIV RNA of at lest 1 log during the 28-day study. Of these patients, five sustained the reduction in plasma HIV RNA beyond day 28 (2 patients receiving 771 mg/day and 3 patients receiving 1,026 mg/day). Median increases from baseline in CD4+ counts at day 28 were 216 cell/mm3 and 86 cell/mm3 in the 771-mg and 1,026-mg groups, respectively. After oral administration, median nelfinavir plasma concentrations on day 28 reached a maximum at 1 hour (2,966 ng/mL) in the 771-mg group and at 3 hours (3,157 ng/mL) in the 1,026-mg group. Data for 22 patients were included in the safety analysis; 12 patients (55%) reported at least one grade 2 or worse (moderate, severe, or very severe) adverse event. The most common grade 2 or worse adverse event was diarrhea, reported by two patients (20%) receiving 771 mg/day and seven patients (70%) receiving 1,026 mg/day; followed by nausea, flatulence, asthenia, and headache (each reported in 1 patient [10%] in the 771-mg group) and dizziness (reported in 1 patient [10%] receiving 1,026 mg/day). In the small subgroup (n = 6) who continued taking nelfinavir for longer periods (between 8 and 15 months), virologic responses were sustained in the majority of patients with good tolerability. Nelfinavir is an active HIV-protease inhibitor with favorable pharmacokinetics, good tolerability, and sustained antiviral effects. Results of this early phase I/II dose-ranging study provided data for the safety and antiretroviral activity of nelfinavir and led to the selection of higher doses for phase II/III trials to further optimize virologic and immunologic responses.

Phase I clinical and pharmacology study of 502U83 given as a 24-h continuous intravenous infusion.

502U83 is an arylmethylaminopropanediol that displays significant antitumor activity in a number of murine and human tumor-model systems. In the present phase I study, a 24-h continuous intravenous infusion of this agent was given every 28 days to patients with advanced or refractory solid tumors. In all, 46 patients received a total of 96 cycles of 502U83 at doses ranging from 25 to 8,000 mg/m2. No significant hematologic, gastrointestinal, or neurologic toxicity was observed. At doses of 2,000 mg/m2 and higher, prolongation of the corrected QT interval on ECG was evident in most patients but was completely reversible, was not associated with arrhythmias, and was not dose-limiting. Dose-limiting pulmonary toxicity characterized by acute onset of dyspnea, severe hypoxemia, interstitial pulmonary edema, and death occurred in three patients treated at the highest dose levels. Plasma concentrations of 502U83 and its metabolites were measured by high-performance liquid chromatography. The 502U83 maximal concentration (Cmax) and area under the concentration-time curve (AUC) were proportional to the delivered dose; however, substantial interpatient variability in total body clearance was noted at all dose levels. Significant conversion of 502U83 to two glucuronide metabolites was detected. Metabolite concentrations were highest in the three patients who succumbed to pulmonary toxicity, although the precise contribution of these metabolites to the observed toxic effects is unknown. In view of the unfavorable clinical profile of QTc prolongation and pulmonary toxicity produced by 502U83, further clinical development of this agent has been suspended.

Initial clinical trial and pharmacokinetics of Thymitaq (AG337) by 10-day continuous infusion in patients with advanced solid tumors.

PURPOSE: To establish the maximum tolerated dose (MTD), dose-limiting and other major toxicities and the major pharmacokinetic parameters of a 10-day infusion of the nonclassical antifolate Thymitaq. METHODS: The drug was given by 10-day infusion via a portable pump. The starting dose was 286 mg/m2 per day with escalation to 572 and 716 mg/m2 per day. Thymitaq in plasma was assayed by a validated isocratic reverse-phase HPLC assay with detection at 273 nm. RESULTS: The dose of 716 mg/m2 per day x 10 was considered too high as none of three patients completed a 10-day infusion and two of three developed grade IV myelotoxicity. At 572 mg/m2 per day three of four patients completed a 10-day infusion. Dose-limiting myelosuppression was seen in one of four but owing to a high incidence of thrombotic phenomena, no further patients were added. CONCLUSION: Continuous 10-day infusions of Thymitaq should be limited to low doses until further studies can be done.

Phase I study of AG2034, a targeted GARFT inhibitor, administered once every 3 weeks.

PURPOSE: To identify a recommended phase II dose for the second generation glycinamide ribonucleotide transformylase (GARFT) inhibitor, AG2034, administered by intravenous bolus every 3 weeks without folate supplementation and to describe AG2034 pharmacokinetics. METHODS: Adults with advanced malignancies were enrolled in cohorts of three per dose level with expansion to six upon observation of dose-limiting toxicity (DLT). The maximum tolerated dose (MTD) was defined as the dose at which two of up to six patients experienced DLT. Upon identification of an MTD and evidence of cumulative toxicity, a lower intermediate dose was explored as a candidate phase II dose. AG2034 plasma concentrations were measured using an ELISA assay. RESULTS AND CONCLUSIONS: The recommended phase II dose is 5.0 mg/m2. DLTs were anemia, thrombocytopenia, mucositis, diarrhea, hyperbilirubinemia, fatigue, and insomnia. Toxicities were modestly cumulative over three courses. Pharmacokinetic analysis showed a dose-AUC0-24 relationship and a progressive increase in AG2034 AUC0-24 over three courses. Both pharmacokinetic and pharmacodynamic factors may contribute to the modest cumulative toxicity observed with AG2034.

Phase II trial of piritrexim and DTIC using an alternating dose schedule in metastatic melanoma.

A Phase II trial was conducted in patients with metastatic malignant melanoma with DTIC 250 mg/m2 intravenously for 5 days alternating monthly with Piritrexim (PTX) using an intermittent, low-dose oral administration schedule. PTX was administered at a starting dose of 25 mg orally three times per day for 5 days weekly for 3 weeks followed by 1 week of rest. Twenty-one patients were entered into the study. Among the 17 patients assessable for response, 1 patient had a minor response, and 3 patients had stable disease. No partial or complete response were observed. Toxicity was tolerable and consistent mainly of myelosuppression. Using this alternating dose schedule, PTX and DTIC produced little response in metastatic melanoma.

Short-term measures of relative efficacy predict longer-term reductions in human immunodeficiency virus type 1 RNA levels following nelfinavir monotherapy.

We calculated the relative efficacy of treatment, defined as the rate of decline of virus levels in plasma during treatment relative to the rate of decline during highly potent combination therapy, in human immunodeficiency virus type 1 (HIV-1) patients treated for 56 days with different doses of the protease inhibitor nelfinavir. Relative efficacies based on the rate of decline of HIV-1 RNA levels in plasma over the first 14 to 21 days correlated with drug dose and viral load reduction by day 56. Calculation of relative treatment efficacies over the first 2 to 3 weeks of treatment can allow rapid assessment of new antiretroviral agents and dosing regimens, reducing the need to keep subjects in clinical trials on monotherapy for prolonged periods of time. Relative efficacy may also serve as a measure of treatment efficacy in patients in initiating established therapies.

Phase II trial of oral piritrexim in advanced, previously treated transitional cell cancer of bladder.

UNLABELLED: Oral piritrexim (PTX), a second generation antimetabolite, has been shown to be an active agent against methotrexate refractory transitional cell cancer (TCC) of the bladder in phase I trials. We conducted a phase II trial of this drug in patients with TCC of the bladder who failed a first line chemotherapy regimen. METHODS: Oral PTX was started at the dose of 25 mg three times per day for 5 days weekly for 3 weeks followed by one week of rest. If this was tolerated the dose was increased to 50 mg three times a day. Patients were monitored for response rate and toxicity. RESULTS: Seventeen patients were entered into the trial. Two patients did not complete the required 2 courses of treatment to be evaluable. There were 13 evaluable patients. Among the 13 no one achieved a complete response (CR), however, there were 3 partial responses (PRs = RR: 23%) and 5 stable diseases (SDs). The responses lasted 2, 8 and 14 months. The major dose-limiting toxicity was myelosuppression. Two patients died on treatment. One death was due to neutropenic fever and the cause of death in the second patient is thought to be a cerebral vascular accident (CVA). CONCLUSION: PTX is an active drug in the treatment of TCC of the bladder. Bone marrow suppression is the most common dose-limiting toxicity. In view of the observed responses and toxicities in this study and other studies, we suggest that the role of PTX be further investigated in the following clinical settings: 1. Palliative initial treatment in patients with TCC of the bladder who are not candidates for more aggressive chemotherapy. 2. As first line chemotherapy in combination with other active drugs.