Multicenter phase II study of trabectedin in patients with metastatic castration-resistant prostate cancer

BACKGROUND

This multicenter phase II trial evaluated the efficacy and safety of trabectedin in metastatic castration-resistant prostate cancer (CRPC).

PATIENTS AND METHODS

Two schedules were evaluated in three cohorts: weekly as 3-h i.v. infusion at 0.58 mg/m(2) for 3 out of 4 weeks (Cohort A, n = 33), and every 3 weeks (q3wk) as 24-h infusion at 1.5 mg/m(2) (Cohort B1, n = 5) and 1.2 mg/m(2) (Cohort B2, n = 20). The primary end point was prostate-specific antigen (PSA) response; secondary end points included safety, tolerability and time to progression (TTP).

RESULTS

Trabectedin resulted in PSA declines ≥ 50% in 12.5% (Cohort A) and 10.5% (Cohort B2) of patients. Among men pretreated with taxane-based chemotherapy, PSA response was 13.6% (Cohort A) and 15.4% (Cohort B2). PSA responses lasted 4.1-8.6 months, and median TTP was 1.5 months (Cohort A) and 1.9 months (Cohort B2). The dose of 1.5 mg/m(2) (approved for soft tissue sarcoma) given as 24-h infusion q3wk was not tolerable in these patients. At 1.2 mg/m(2) q3wk and 0.58 mg/m(2) weekly, the most common adverse events were nausea, fatigue and transient neutropenia and transaminase increase.

CONCLUSIONS

Two different trabectedin schedules showed modest activity in metastatic CRPC. Further studies may require identification of predictive factors of response in prostate cancer.

Effect of EGFR inhibition with cetuximab on the efficacy of paclitaxel in previously treated metastatic urothelial cancer

243

Background: The benefit of salvage chemotherapy such as weekly paclitaxel (TAX) is modest in metastatic (met) urothelial ca, with median TTP of ≤3 months and ORR of 10% (95% CI 4-18% [combined results, Vaughn 2002; Joly, 2009]). Cetuximab (CET) is a monoclonal antibody against the epidermal growth factor receptor (EGFR). High-grade urothelial cancer overexpress EGFR. We conducted a multicenter randomized, noncomparative phase II study to measure the efficacy of CET ± TAX in patients (pts) with previously treated met urothelial cancer.

Methods: Pts with met urothelial cancer who received one line of chemotherapy in the adjuvant, neoadjvuant, or met setting were enrolled. Pts were randomized to CET 250mg/m2 (after 400 mg/m2 load) ± TAX 80 mg/m2 weekly. A cycle was 4 weeks (wks). Response (RECIST) was assessed by imaging every 8 wks. We used early progression to assess futility (Litwin Stats Med 2007). Either arm would close if 7 of the initial 15 pts in that arm progressed at the first disease evaluation. Either arm would be considered promising if ≥9/28 patients had PFS>16 wks (90.4% power to detect an improvement in Median [Med] PFS from 8 to 16 wks with a 7.1% type 1 error).

Results: We enrolled 39 evaluable pts (30 male). Median age was 69 years (range 49-79). All pts received prior platinum-based chemotherapy. CET arm closed after 9 of the first 11 pts progressed by 8 wks (ASCO GU 2009). CET-TAX arm completed full accrual (28 pts), of which 11 had visceral disease and 13 received chemo for met disease. 10/28 pts had PFS>16 wks. Overall RR was 28.5%, (8/28 pts, 95% CI 13-49%) (2 CR, 6PR). 4 additional pts had unconfirmed PR. 2 pts have maintained PR 3 and 4 months after discontinuing CET-TAX. Med PFS for the CET-TAX was 115 days (16 weeks)(95% CI 58-174 days). Med PFS for pts with visceral disease was 84 days (95%CI 50-NR). Med PFS for pts who received prior chemo for met disease was 142 days (95% 58-NR). Med number of cycles for the CET-TAX was 3 (range 0-25). Grade 3 AEs occurring in more than 2 pts were rash (5), fatigue (4), anemia (4), low magnesium (3).

Conclusions: EGFR inhibition with CET appears to augment the antitumor activity of TAX in pts with previously treated urothelial cancers. The CET-TAX combination merits further study to establish its role in treatment of urothelial cancers.

[Table: see text]

Randomized phase II multicenter study of the efficacy and safety of sunitinib on the 4/2 versus continuous dosing schedule as first-line therapy of metastatic renal cell carcinoma: Renal EFFECT Trial

LBA308

Background: In a randomized phase III trial, sunitinib 50 mg/d on Schedule 4/2 (4 wk on treatment [Tx], 2 wk off) showed superior progression-free survival (primary endpoint) to IFN-α (11 vs. 5 mo; p<0.001) as first-line metastatic renal cell carcinoma (mRCC) therapy with a median overall survival (OS) of >2 yr (Motzer 2009). Continuous dosing of sunitinib 37.5 mg has demonstrated antitumor activity with a manageable safety profile in first- and second-line mRCC (Barrios; Escudier, 2009).

Methods: This randomized phase II trial compared sunitinib 50 mg/d on Schedule 4/2 (Arm A) vs. 37.5 mg continuous once-daily dosing (Arm B) in first-line mRCC. Eligible patients (pts) had clear cell locally recurrent or mRCC; measurable disease; and Karnofsky performance status ≥70%. Randomization (1:1) was stratified by MSKCC risk groups. Sunitinib was continued until progression, unacceptable toxicity, or up to 2 yr. The primary endpoint was time to tumor progression (TTP) by Kaplan-Meier estimate. Secondary endpoints included objective response rate (ORR), OS, and adverse events (AEs).

Results: Between January 2007 and June 2008, 292 pts were randomized. As of October 2010, 289 pts had received sunitinib, and all pts were off therapy. Median age was 62 yr. 65% were male. By MSKCC criteria, 28%, 61%, and 11% were favorable, intermediate, and poor risk, respectively. Pts received a median 4 and 5 Tx cycles in Arms A and B, respectively; median relative dose intensity was 90.8% and 77.5%. Dose delays, reductions, and interruptions occurred in 30% vs. 13%, 36% vs. 43%, and 65% vs. 62%, respectively; 11% and 15% discontinued due to Tx-related AEs. Median TTP was 9.9 vs. 7.1 mo in Arms A and B, respectively (HR=0.773, 95.1% CI, 0.572, 1.044; p=0.090). ORR was 32.2% vs. 28.1% (p=0.444). Median OS was 23.1 vs. 23.5 mo (p=0.615). The most common Tx-related AEs were fatigue (both 62%), nausea (56% vs. 49%), and diarrhea (56% vs. 64%).

Conclusions: In this randomized phase II mRCC trial, there was a trend toward inferior TTP with continuous dosing. ORR, OS, and AE profiles were similar for the approved sunitinib 50 mg/d dose on Schedule 4/2 vs. 37.5 mg continuous dosing.

[Table: see text]

A phase I study of temsirolimus (TEM) and bryostatin (BRYO) in patients with metastatic renal cell carcinoma (RCC)

5111

Background: TEM, an inhibitor of mTOR complex 1 (TORC1), is approved for the treatment of metastatic RCC. BRYO inhibits protein kinase C, a downstream effector of mTOR complex 2 (TORC2). We observed additive effects of TEM and BRYO against RCC in vitro. Methods: Four cohorts of 3–6 patients (pts) received weekly BRYO (20 mcgm/m2) and TEM (10, 15, 25, or 37.5 mg,) in 28 day cycles. DLT was defined as 1st cycle toxicity ≥ grade 3. Results: Twenty-three pts have been enrolled. Eighteen pts had RCC: clear cell (12), papillary (3), clear cell with sarcomatoid/spindle features (2), unclassified (1), Among RCC pts, 3 had no prior therapy. 15 had a median of 2 prior therapies (immunotherapy, TKIs, and/or bevacizumab). To date, 22 pts have received 103 cycles across 4 dose levels. Five non-RCC pts (4 sarcoma, 1 paraganglioma) received up to 3 cycles of treatment. Two of these pts (both had prior cytotoxic therapy) experienced DLT at 15 mg (Gr 3 neutropenia and Gr 3 hypophosphatemia) Subsequently, pts with prior cytotoxic therapy were excluded. One additional non-RCC pt (prior radiation) experienced DLT (Gr 3 neutropenia) at TEM 37.5 mg. Among RCC pts, there were no 1st cycle DLT's. Significant toxicities during later cycles included Gr 3/4 thrombosis at TEM 37.5 mg (2), Gr 4 thrombus/Gr 4 LV dysfunction at TEM 15 mg (1), and Gr 3 dyspnea/Gr 3 pneumonitis at TEM 10mg (1). Gr 4 hypercholesterolemia (1) and Gr. 4 triglyceride elevation (1) were seen at TEM 37.5 mg, both reversed with treatment. One RCC pt withdrew prior to receiving treatment. Of the 17 remaining RCC pts, 3 had PRs and 9 had SD. One treatment naïve pt (TEM 15 mg) continues with PR for 2+ years after discontinuing treatment. One pt (had progressed on sunitinib) continues in a PR at 14+ months. Twelve pts received ≥4 cycles and 3 received >10 cycles. PR was seen in both clear cell and papillary histologies. Median PFS was 7.8 months for all pts and 5.7 months for previously treated pts. Two pts, both with PR, remain on treatment, having received 18 and 8 cycles. Conclusions: The TEM/Bryo combination is feasible for multiple cycles on a weekly schedule at full doses of each agent with durable PR and SD in RCC refractory to other therapies. Enrollment continues to further characterize safety and efficacy.

[Table: see text]

Sunitinib therapy for patients (pts) with metastatic renal cell carcinoma (mRCC): Updated results of two phase II trials and prognostic factor analysis for survival

5095

Background: Two single-arm phase 2 trials reported a 42% objective response rate (ORR) with sunitinib as second-line therapy in mRCC pts (JAMA 2006;295:2516–24). Efficacy results were updated and an analysis of prognostic factors for survival was performed on pooled data. Methods: Eligibility criteria and treatment plan were nearly identical for both trials. Pts with mRCC who failed =1 prior cytokine-based therapy received sunitinib in repeated 6-week cycles of 50 mg/day orally for 4 weeks, followed by 2 weeks off treatment. Response was assessed by investigators according to RECIST. Pretreatment clinical and biochemical features were examined for prognostic factors by univariate and multivariate analysis (p<0.05 significance level was used in the backward stepwise selection procedure). Results: Updated efficacy data for 168 evaluable pts showed an ORR of 45% (95% CI: 39%, 54%), median progression-free survival (PFS) of 8.4 months (95% CI: 7.9, 10.7), and median overall survival (OS) of 22.3 months (95% CI: 14.8, 36.0). Twenty pts remain on treatment with sunitinib with the longest pt on the drug for >3.5 years with partial response for >3 years. The median duration of response was 11.6 months (95% CI: 9.9, 15.2), and included 1 pt with a complete response for >2 years. The proportion of pts alive at 2 years is 48%. Final prognostic factors for survival in the multivariate model were ECOG PS 0 vs. =1 (p=0.0034); time interval from diagnosis to sunitinib treatment =1 yr vs. <1 yr (p=0.0002); hemoglobin =13 vs. <13 g/dL for males and =11.5 vs. <11.5 g/dL for females (p=0.0002). Conclusions: Median survival is nearly 2 years, which compares favorably to the historical experience (12.7 months) in second-line therapy with other agents (JCO 2004;22:454–63). The influence of sunitinib therapy on patient survival is being investigated in a randomized phase 3 trial compared to interferon-a in first-line therapy for mRCC. Further study of prognostic factors to sunitinib therapy is warranted in the first-line setting.

No significant financial relationships to disclose.

Exposure-response of sunitinib in metastatic renal cell carcinoma (mRCC): A population pharmacokinetic/pharmacodynamic (PKPD) approach

5027

Background: Sunitinib malate (SU) is an oral, multitargeted tyrosine kinase inhibitor of VEGFRs and PDGFRs, and has shown substantial antitumor activity in mRCC (Motzer et al, JAMA 2006 and ASCO 2006). This analysis describes SU, and total drug (TD; SU+SU12662 [active metabolite]) exposure-response relationships in mRCC using a population PKPD approach. Methods: PK and efficacy data from 3 studies (phase II and III) of SU (25–62.5 mg/day; 4 wks dosing followed by 2 wks off) in treatment-naïve (N=44) and cytokine-refractory mRCC pts (N=148) were analyzed. SU and SU12662 concentrations were fitted to a population PK model (a 2- compartment model for both parent and metabolite). Estimates of pt PK were used to calculate steady-state Area Under the Curve (AUCss) for SU, SU12662 and TD, which were used as the exposure measure in a PKPD analysis of partial response (PR) rates, time to tumor progression (TTP), overall survival (OS), and tumor volume changes. Results: The probability of a PR for cytokine-refractory pts increased with increasing AUCss for SU and TD. The odds-ratio suggested a 2.6-fold increase in PR frequency for each unit increase in AUCss. Longer TTP and OS were also noted in pts with high SU and TD AUCss. In treatment-naïve pts on SU, there was very little observed tumor progression or death (only 5 pts progressed and only 1 death) limiting the ability to analyze exposure-response. A tumor growth dynamics model (developed to describe changes in tumor volume [by CT or MRI] in response to treatment, as a function of AUCss) provided a good description of tumor volume changes with SU for both treatment-naïve and cytokine-refractory pts. Efficacy was not related to baseline tumor volume, gender, or race. Based on this model, clinical trial simulations assuming perfect pt compliance predict that 62% of pts would achieve a PR with SU 50 mg/day. Conclusions: SU and TD AUCss correlated significantly with the probability of a PR in cytokine- refractory pts, and longer TTP and OS. Limited data were available for treatment-naïve pts. The tumor growth dynamics model provided a good description of tumor volume changes with SU for both populations. This exposure-response analysis indicates that increased exposure to SU is associated with clinical benefit.

[Table: see text]

Preliminary results of a phase I study: A chimeric monoclonal anti IL-6 antibody CNTO 328 in combination with docetaxel in patients with hormone refractory prostate cancer

15521

Background: High serum levels of pro-inflammatory cytokine IL-6 may impact the progression and survival of metastatic hormone refractory prostate cancer (HRPC). CNTO328, an anti IL-6 monoclonal antibody, inhibited prostate tumor growth in several preclinical xenograft mouse models. Methods: This Phase 1, open label study evaluates the safety, pharmacokinetics (PK), and pharmacodynamics of CNTO328 at three dose levels (6mg/kg q2 weeks, 9mg/kg q3 weeks and 12mg/kg q3 weeks) in combination with docetaxel (75mg/m2 q3 weeks) in men with metastatic HPRC. C-reactive protein (CRP), a surrogate biomarker of serum IL-6, and circulating tumor cells (CTC) are evaluated. Results: Eight patients with a median baseline PSA value of 56.8 ng/ml (range 13.6- 436.9 ng/ml) were treated in the first cohort (6 mg/kg CNTO328 q2 weeks in combination with docetaxel 75 mg/m2 q3 weeks). At baseline, 6 patients (75%) had detectable CRP and 6 patients had detectable CTCs. The median number of CNTO328 doses and docetaxel cycles administered was 6 (CNTO328: range 3 to 11 doses; docetaxel: range 3 to 13 cycles). No first-cycle DLT was observed for this combination. Three patients discontinued treatment due to docetaxel-related grade 3 adverse events (deep vein thrombosis, hyperbilirubinemia, and nail changes) after 6, 11, and 13 cycles of docetaxel, respectively. Serum CRP decreased to below detectable levels 7 days after the first dose of CNTO328 in all patients with measurable values at baseline and remained undetectable throughout treatment. Two patients with post-treatment CTC values showed CTC reduction from 82 to1, and 127 to1, respectively. Six of 8 patients had = 50% PSA reductions and all had stable or improved bone scans and/or CT scans. PK of CNTO328 and docetaxel, alone and in combination, will be presented. Conclusions: Thus far, anti-IL6 therapy with CNTO328 at 6mg/kg q2 weeks in combination with docetaxel 75mg/m2 q3 week has been feasible and tolerable. Complete suppression of CRP and PSA reduction provide evidence of biological and anti-tumor activity of this approach and support further testing.

[Table: see text]

Sunitinib malate (SU) plus interferon (IFN) in first line metastatic renal cell cancer (mRCC): Results of a dose-finding study

5101

Background: Sunitinib malate is an oral, multitargeted tyrosine kinase inhibitor of VEGFRs and PDGFRs with anti-tumor activity in mRCC patients previously treated with cytokines (JAMA, 2006;295:2516). A phase 3 randomized trial showed superiority for SU over IFN in first-line mRCC (PROC ASCO 24,18S, 2006). Dose and safety for SU combined with IFN was investigated in this phase I trial. Methods: Patients (pts) with previously untreated clear-cell mRCC received SU in repeated 6-week cycles of 50 or 37.5 mg/day orally for 4 weeks, followed by 2 weeks off treatment. IFN was given continuously, starting at 3 MU SC 3x/week with intrapatient dose escalation weekly as tolerated, to a maximum of 9 MU. Pts not tolerating a dose combination received lower doses of SU or IFN, or had dose interruptions. Doses of SU plus IFN were considered tolerable if = 4/6 pts completed 2 cycles without dose reduction or interruption. Results: 25 pts were enrolled; 19 are evaluable for safety/response. 6 pts who started treatment at 37.5 SU and 3 MU IFN are too early. The median age of the 19 pts (16 M: 3 F) was 63 years (range 45–77). MSKCC risk group (JCO 20:289–96, 2002) was 37% good and 63% intermediate. 12 pts started treatment with SU 50 mg and dose escalated IFN to 6 or 9 MU TIW. 13 pts started treatment with SU 37.5 mg and dose escalated IFN at 3 MU or to 6 MU TIW. 4 of 19 pts tolerated two cycles. 68% of pts had dose interruptions of SU; 90% of pts had dose interruptions of IFN. 15/19 pts had grade 3 toxicity, 1 pt had grade 4 hypertension and 1 pt grade 5 toxicity (myocardial infarction). Most common grade 3 toxicities were neutropenia (26%), fatigue (26%), and hand-foot syndrome (16%). Although response was not a primary endpoint, at a median of 3 cycles, there were 2 PR, 14 SD, 2 PD and 1 pt was not evaluable. Conclusions: The adverse events seen with combination SU and IFN in mRCC, neutropenia and fatigue, were similar to those seen with single agent SU and IFN, and resulted in frequent dose modifications and interruptions. The safety and efficacy of 37.5 mg sunitinib and 3 MU IFN is being evaluated.

No significant financial relationships to disclose.

Phase I/II study of sunitinib malate in combination with gefitinib in patients (pts) with metastatic renal cell carcinoma (mRCC)

5097

Background: Sunitinib malate is an oral, multitargeted tyrosine kinase inhibitor of VEGF- and PDGF- receptors with substantial antitumor activity against mRCC (JAMA 2006;295:2516). This study was conducted to evaluate the safety and efficacy of sunitinib in combination with gefitinib, an EGF-receptor inhibitor. Methods: Eligibility included mRCC with clear cell component. The phase 1 part of the study was conducted to determine the maximum tolerated dose (MTD) of sunitinib in combination with gefitinib, and subsequently pts were enrolled in the phase 2 part to further evaluate safety and antitumor activity. Pts were treated with sunitinib at assigned dose level (37.5 mg or 50 mg) orally daily for 4 weeks on, followed by 2 weeks off (Schedule 4/2) and gefitinib at 250 mg daily. The primary endpoint for the phase 2 part of the study was objective response according to RECIST. Results: Forty-two pts were enrolled; 11 pts in phase 1 and 31 pts in phase 2. Median age was 65 years (range: 29–78) and 35 pts (83%) had =2 metastatic sites. Twenty-eight pts (67%) had prior cytokine therapy, 11 pts (26%) had no prior cytokine therapy, and 3 pts (7%) received prior vaccine therapy. Two dose limiting toxicities (DLTs) were observed at the 50-mg dose level (grade 3 fatigue and grade 2 ejection fraction decline), and 37.5 mg on Schedule 4/2 in combination with gefitinib 250 mg daily was determined to be the MTD. The median duration on treatment was 8.3 months for phase 1. Thirty-six pts are evaluable for response and 6 are too early. Eleven pts (30%) achieved a partial response and 15 pts (42%) stable disease. The most common grade 3 treatment-related adverse events observed in phase 1 were diarrhea and nausea (n=2) and for phase 2 were diarrhea (10%) and gastrointestinal hemorrhage (6%). Two pts from phase 2 were withdrawn from the study due to treatment-related adverse event; ejection fraction decline and cardiac arrhythmia, both of which were reversible after treatment discontinuation. Conclusions: The study established dose and feasibility for sunitinib in combination with gefitinib. Early evaluation of the data suggests tolerability for the combination and relative efficacy data compared to sunitinib monotherapy will be assessed with longer patient follow-up.

No significant financial relationships to disclose.

Pharmacokinetics (PK) and efficacy of sunitinib in patients with metastatic renal cell carcinoma (mRCC)

4531

Background: Sunitinib malate (SU11248) is an oral, multi-targeted tyrosine kinase inhibitor of VEGFR, PDGFR, KIT, FLT3, and RET. Clinical studies have demonstrated efficacy of sunitinib in patients with multiple tumor types including two phase II studies in mRCC, where second-line monotherapy with sunitinib showed a response rate of greater than 40% by RECIST, with an additional ≥25% of pts exhibiting prolonged stable disease. A population PK analysis was performed to assess the exposure-response relationship between PK and tumor volume changes, clinical response, and time to tumor progression (TTP) in these two mRCC studies. Methods: In these two studies, 169 patients with mRCC were treated with sunitinib 50 mg/day for 4 weeks, followed by a 2-week off period (Schedule 4/2). Response to treatment was assessed by measuring tumor volume. Clinical response was assessed using RECIST and TTP using logistic regression and Kaplan-Meier survival analysis. A previously described population PK model of sunitinib and its primary active metabolite SU12662 was updated using additional data from three trials, including the two RCC trials. Using the model and trough plasma concentrations, steady-state AUCs of sunitinib plus SU12662 were estimated for each mRCC patient and tested as a predictor of response. Results: PK profiles were evaluable for 149 patients in the two mRCC trials. Plasma clearance (CL) decreased by an average of 28% in mRCC patients relative to healthy volunteers. Covariates, such as gender, age, and ECOG score also affected CL, however all of these changes were less than the estimated inter-individual variability in CL of 43%. Improved clinical response and longer TTPs were associated with greater AUCs. Within 12 weeks of treatment, mean tumor volume decreased by 24–32% in each trial. Conclusions: Individual patient exposures to sunitinib and SU12662 can be predicted with sparse concentration measurements using population PK analysis, and an exposure-response relationship is evident in mRCC. Dose adjustment is not warranted based upon any evaluated covariate. Over the first 12 weeks of treatment at 50 mg daily on Schedule 4/2, increased exposure was associated with improved clinical response and decreased tumor volumes.

[Table: see text]

A meta-analysis of individual patient data from randomized trials assessing chemotherapy with and without estramustine in patients with castration-refractory prostate cancer

4561

Background: Estramustine phosphate is a mustard-estradiol conjugate, with evidence of both hormonal and non-hormonal effects. In phase II trials, the response rates of microtubule inhibitors are increased when combined with estramustine. Morbidity includes notably thrombosis in about 7% of cases. Whether combining estramustine with chemotherapy increases survival in castration-refractory prostate cancer (CRPC) is still controversial. Methods: Data from all published and unpublished prospective randomized trials assessing chemotherapy + estramustine versus chemotherapy alone in CRPC were sought using electronic database searching, hand searching, and by contacting experts in the field. The primary endpoint was overall survival (OS). The analysis was performed on an intention-to-treat basis. The stratified logrank test was used and an overall hazard ratio (HR) was computed using a fixed effect model. χ2 heterogeneity tests were used to test for statistical heterogeneity. All p-values were two-sided. Multivariate analysis was performed using a Cox model stratified by trial. Results: Individual data were obtained from all 5 randomized trials conducted in the PSA era that had been identified (n = 610). The control arms consisted of docetaxel (1), paclitaxel (1), ixabepilone (1), and vinblastine (2). With a median follow-up of 2.8 years, 510 deaths had occurred. OS was significantly better in the estramustine arm (HR = 0.82 [95% CI: 0.69–0.97]; p = 0.02). Overall, the risk reduction (RR) of death related to estramustine was 18% (± 8). There was no significant interaction (p = 0.66) between the RR of trials using vinblastine (RR = 15% [± 12]) and in those using taxanes or ixabepilone (RR = 21% [± 11]). The estimated 1-year OS rate was 57% and 50% in the estramustine arm and in the control arm, respectively. The 18-months OS rate was 43% and 35%, respectively. There was no interaction between the effect of estramustine and age, performance status, or serum PSA in the Cox model. Conclusions: Combining estramustine with chemotherapy increases OS over chemotherapy alone in patients with castration-refractory prostate cancer.

[Table: see text]

Phase I study of intravenous CCI-779 in combination with bryostatin-1 in solid tumors

3067

Background: mTOR regulates translation of messenger RNA critical for angiogenesis and cell growth. CCI-779 inhibits mTOR signaling through p70S6 kinase (S6K), which phosphorylates the ribosomal S6 protein (S6). CCI-779 is active in renal carcinoma (RCC) and other solid tumors. Based on our finding that bryostatin-1 (bryo) inhibits S6K, and that CCI-779 + Bryo additively inhibit S6K and RCC growth in vitro, we initiated a phase I trial to determine the maximum tolerable (MTD) doses and dose-limiting toxicities of this novel combination in patients with solid tumors. Methods: Bryo (20 μg/m2) was administered over 60 minutes IV followed by CCI-779 (10 and 15 mg, planned escalation to 75 mg) IV over 30 minutes, both weekly for 3 of 4 weeks. Serum and peripheral blood mononuclear cell (PBMC) samples were collected for analysis of pharmacokinetics and markers of mTOR inhibition (phospho-S6 and p21waf1). Results: Nine patients (median age 57, 6 RCC, 2 sarcoma and 1 neuroendocrine) are evaluable for toxicity (total cycles=27 cycles, median 4, range 1–7) at the initial 2 dose levels (Bryo 20 μg/m2, CCI-779 10 mg and 15 mg). Cycle 1 toxicity includes grade 3 hypophosphatemia and myelosuppression in one patient each and grade 2 fatigue, stomatitis, and anemia. One patient developed reversible grade 3 pneumonitis after 7 cycles. Of 7 patients with therapy-resistant disease, 5 (4 RCC and 1 sarcoma) had stable disease lasting up to 7 months. A therapy-naive patient with RCC has 23% tumor reduction after 2 cycles at dose level 2 (CCI-779=15 mg). PBMC proteins from 5 patients show consistent decreases in phospho-S6 at 2–6 hours-post treatment compared with pre-treatment baseline measurement, with recovery by 24–72 hours after dosing. In parallel with inhibition of phosphorylation of S6, PBMC levels of p21waf1 were completely inhibited in all 5 patients. Conclusions: The combination of bryo and CCI-779 is feasible, with antitumor activity in RCC and mTOR pathway inhibition observed at submaximal doses. Dose escalation is continuing.

No significant financial relationships to disclose.

Modulation of endogenous beta-tubulin isotype expression as a result of human beta(III)cDNA transfection into prostate carcinoma cells

Increases of individual beta tubulin isotypes in antimicrotubule drug resistant cell lines have been reported by several laboratories. We have previously described elevations in beta(III)and beta(IVa)isotypes in estramustine and paclitaxel resistant human prostate carcinoma cells. To investigate further the function of beta tubulin isotypes in antimicrotubule drug response, human prostate carcinoma cells that normally have very low to undetectable levels of beta(III)were stably transfected with beta(III)cDNA in pZeoSV system. An 18 bp haemagglutinin (HA) epitope tag was added at the 3' end prior to cloning into the vector. Cells were transfected with pZeoSV or pZeoSV-beta(III)plasmids and selected in the presence of Zeocin. Immunofluorescent staining of the transfectant cells have shown significant expression and incorporation of HA-tagged beta(III)tubulin into cellular microtubules. Quantitation of Western blots revealed the HA-tagged beta(III)levels to be approximately 7-fold higher than the vector control cells. RT-PCR analysis confirmed the increase at the transcript level and also revealed a collateral increase of beta(II)and beta(IVb)transcripts. Cell viability assays indicated that sensitivity of beta(III)transfected cells to various antimicrotubule agents was similar to vector transfected cells: IC50 values for estramustine, paclitaxel, colchicine and vinblastine were 4 microM, 4 nM, 22 nM and 2 nM, respectively for both cell lines. Thus, overexpression of beta(III)isotype in human prostate carcinoma cells by stable transfection failed to confer antimicrotubule drug resistance to these cells. Counterregulatory increases of endogenous beta(II)and beta(IVb)tubulin isotypes in these beta(III)transfected cells may be a compensatory mechanism used by the cells to overcome the effects of elevated beta(III)levels on the cellular microtubules. These results highlight the difficulty in isolating the contribution of single tubulin isotypes in drug response studies.

Toxicity and response evaluation of the interferon inducer poly ICLC administered at low dose in advanced renal carcinoma and relapsed or refractory lymphoma: a report of two clinical trials of the Eastern Cooperative Oncology Group

PURPOSE

Phase II studies were conducted to evaluate the safety and efficacy of the interferon inducer Poly ICLC at low doses in advanced renal cancer and relapsed or refractory lymphoma.

PATIENTS AND METHODS

Twenty-nine patients with advanced renal carcinoma and eleven patients with lymphoma were treated with poly ICLC. Patients received 0.25 mg/m2 of poly ICLC intravenously twice weekly three days apart until progression or unacceptable toxicity.

RESULTS

There were no objective responses. Six patients with renal carcinoma had stable disease as best response with one patient receiving 62 weeks of therapy. Toxicity included grade 3 anemia in 8 patients and grade 4 anemia in one patient. All patients were anemic prior to entry with a median grade 2 anemia at baseline. Grade 4 neutropenia, thrombocytopenia and injection site pain occurred in one patient each. Grade 3 fever, chills or fatigue occurred in four, three, and three patients respectively. Any grade fever occurred in 10 patients (25.6%) and any grade chills occurred in 9 patients (23.1%).

CONCLUSION

Poly ICLC at this dose and schedule is well tolerated in both patient populations and is inactive in renal carcinoma.

Paclitaxel and docetaxel in prostate cancer

Although their ultimate value in prostate cancer therapy remains to be defined in randomized trials, docetaxel and paclitaxel are active agents in HRPC. Combination therapies using either of these taxanes plus oral EMP show reproducible antitumor activity that appears to be greater and more durable than that of single-agent treatment. Although the optimal combination and schedule have not been determined, weekly paclitaxel and EMP and docetaxel given every 3 weeks or by weekly infusion with EMP are useful treatment options for patients with progressive HRPC. The gastrointestinal toxicity of EMP has been reduced by intermittent rather than continuous administration, and other toxicities may be reduced further by use of intravenous EMP. Although there has been progress, the median time to progression of 5 to 6 months for current taxane-based therapies suggests that they will not have major impact on overall survival for patients with HRPC. Greater benefit may be possible earlier in the course of prostate cancer, and the activity of the taxane-EMP combinations is sufficient to justify clinical trials of adjuvant or neoadjuvant chemotherapy for selected groups of patients with locally advanced and poor-prognosis tumors. Armed with many new molecularly targeted agents that may interact favorably with taxanes, it should be possible to build on current antimicrotubule regimens to improve activity in HRPC. Taxane-EMP combinations provide a platform on which to test additional agents that may enhance the apoptotic response or circumvent cellular stress adaptations that confer drug resistance. Further elucidation of signaling pathways that regulate microtubule dynamics and programmed cell death after exposure to microtubule inhibitors would provide a more rational guide for integrating specific inhibitors of signal transduction with current taxane-based therapies. Pharmacokinetic and pharmacodynamic studies will play a key role in the development of future taxane-based therapies for prostate cancer.

Phase II evaluation of menogaril in advanced prostate cancer: Eastern Cooperative Oncology Group EST P-A885

Menogaril is a semisynthetic anthracycline that is less cardiotoxic than doxorubicin in a preclinical model. We conducted a phase II trial to determine the activity of menogaril in hormone-refractory prostate cancer. Between October 1985 and November 1987, 32 eligible patients were enrolled and were divided into good- and poor-risk categories, the latter being defined by prior radiotherapy to less than one third of the marrow-containing skeleton. Good-risk patients received a starting dose of 200 mg/m2 by 60-minute IV infusion, whereas the poor-risk patients received 160 mg/m2. Treatment was repeated every 3 weeks until disease progression. Menogaril caused leukopenia in 90% of patients, of whom 47% had grade III or IV toxicity. Thrombocytopenia was uncommon and mild, with only three patients (9%) experiencing grade II toxicity. Nonhematologic toxicity included mucositis (9%), and mild weight loss in 33% of patients. Nine patients (28%) had stable disease of 3 or more months' duration. There were no objective partial or complete responses. The median time to progression for the entire group was 10 weeks, and the median survival time for all patients was 24 weeks. Because of appreciable toxicity and limited antitumor activity, further study of menogaril cannot be recommended in hormone-refractory prostate cancer.

Phase I pharmacokinetic trial of perillyl alcohol (NSC 641066) in patients with refractory solid malignancies

Perillyl alcohol (POH) is a monoterpene with anticarcinogenic and antitumor activity in murine tumor models. Putative mechanisms of action include activation of the transforming growth factor beta pathway and/or inhibition of p21ras signaling, leading to differentiation or apoptosis. In this Phase I trial, 17 patients took POH p.o. three times daily for 14 days of each 28-day cycle. The starting dose of POH was 1600 mg/m2/dose, with escalations to 2100 and 2800 mg/m2/dose in subsequent cohorts. Chronic nausea and fatigue were dose-limiting toxic effects at 2800 mg/m2. Grade 1-2 hypokalemia was common at 2100 and 2800 mg/m2. Although POH could not be detected in plasma, two of its metabolites, dihydroperillic acid (DHPA) and perillic acid (PA), were measured in plasma and urine on days 1 and 15 after the first and last doses of POH, respectively. Both area under the concentration versus time curve and peak plasma concentration (Cmax) values increased with dose and exhibited high intersubject variability. Day 15 DHPA Cmax values ranged from a mean +/- SD of 22.6+/-12 microM at 1600 mg/m2/dose to 42.4+/-15.24 microM at 2800 mg/m2/dose. Corresponding mean +/- SD Cmax values for PA were 433.2+/-245.8 and 774.1+/-439.6 microM. One patient treated at the 2800 mg/m2/dose had markedly prolonged plasma levels of both PA and DHPA and developed grade 3 mucositis. POH treatment did not consistently alter the expression of p21ras, rap1, or rhoA in peripheral blood mononuclear cells obtained from patients treated at the highest dose level. The metabolites PA and DHPA did not change expression or isoprenylation of p21ras in MCF-7 breast or DU145 prostate carcinoma cells at concentrations that exceeded those achieved in patient plasma after POH treatment. We conclude that POH at 1600-2100 mg/m2 p.o. three times daily is well tolerated on a 14-day on/14-day off dosing schedule. Inhibition of p21ras function in humans is not likely to occur after POH administration at safe doses of the present oral formulation.

Preliminary results of a bone marrow magnetic resonance imaging protocol for patients with high-risk prostate cancer

OBJECTIVES

To compare the accuracy of a bone marrow magnetic resonance imaging (MRI) protocol in patients at high risk of metastatic disease with radioisotopic bone scans, the standard method for detection of bony metastases in patients with prostate cancer.

METHODS

The study group consisted of 19 men with prostate cancer who underwent a bone marrow MRI between November 1993 and February 1996. This protocol images the marrow of the thoracolumbar spine, sacrum, pelvis, and femurs. Indications for MRI included an equivocal bone scan and/or staging of locally advanced or recurrent disease. The findings on MRI and bone scan were compared and the results correlated with the subsequent clinical patient outcome.

RESULTS

The bone marrow MRI protocol detected metastatic disease in 1 (7%) of 13 patients with negative bone scans. Four patients had an indeterminate bone scan: 2 had true-positive MRIs, 1 a true-negative MRI, and 1 a false-positive MRI on the basis of subsequent clinical follow-up. Two patients with positive bone scans had true-positive MRIs.

CONCLUSIONS

Although not recommended for routine staging, MRI was useful in this study for clarifying an equivocal bone scan. The bone marrow MRI protocol images a high yield volume of the bony skeleton and is fast and economical compared with obtaining many focused MRI scans of these areas separately. These preliminary data suggest that further investigation of its clinical utility for staging locally advanced or recurrent disease is justified.

A phase II study of 5-fluorouracil, leucovorin, and interferon-alpha in the treatment of patients with metastatic or recurrent gastric carcinoma: an Eastern Cooperative Oncology Group study (E5292)

BACKGROUND

Chemotherapy has a limited impact on adenocarcinoma of the stomach. Although biochemical modulation of 5-fluorouracil (5-FU) by leucovorin (LV) and interferon-alpha (IFN-alpha) has improved the outcomes of patients with metastatic colorectal carcinoma compared with 5-FU alone, this approach has not been extensively evaluated in the treatment of advanced gastric carcinoma.

METHODS

Twenty-seven patients with bidimensionally measurable, metastatic gastric carcinoma and an Eastern Cooperative Oncology Group performance status of 0 or 1 received the combination of IFN-alpha (5 million U/m2 administered subcutaneously daily on Days 1-7), LV (500 mg/m2 administered intravenously over 30 minutes immediately after IFN-alpha on Days 2-6), and 5-FU (370 mg/m2 given as an intravenous bolus 60 minutes after LV on Days 2-6), with treatment repeated every 4 weeks. Oral cryotherapy was administered routinely before each dose of 5-FU to reduce the incidence of severe stomatitis.

RESULTS

The median age of the patients was 58 years (range, 20-76), and 22 patients had residual, unresectable primary lesions. The median number of cycles received was 3 (range, 1-11). Of 24 patients who received at least 2 cycles of treatment, 15 (62.5%) did not require dose reduction for toxicity during the initial 2 cycles. The predominant toxicities were gastrointestinal: diarrhea and stomatitis of Grade 3-4 occurred in 28.6% and 35.7% of patients, respectively. Other severe (Grade 3-4) toxicities were granulocytopenia (which occurred in 21.4% of patients) and fatigue (in 10.7%). Fever and flu-like symptoms were common but usually mild. Of 24 patients who were evaluable for response, 3 had partial responses (PR) of 16, 23, and 33 weeks' duration, respectively, for a response rate of 12.5% (95% confidence interval = 2.7-32.4%). Two additional patients had reductions in tumor size sufficient for PR, but scans to document the minimum required response duration of 4 weeks were not obtained before progressive disease occurred. The median progression-free and overall survivals were 2.5 and 7.8 months, respectively.

CONCLUSIONS

Although this regimen can be administered safely with appropriate supportive care to patients with good performance status, it has limited therapeutic activity in patients with advanced gastric carcinoma.

Cisplatin-based chemotherapy for testicular cancer in a patient with spinal muscular atrophy: a case report

Metastatic germ-cell tumors of the testis are highly curable with cisplatin-based chemotherapy. Although cisplatin-based chemotherapy is generally well tolerated and rarely causes severe neurotoxicity, there is little information to guide the treatment of patients with neuromuscular disorders. The authors report the successful treatment of a patient with testicular cancer and spinal muscular atrophy, an inherited degenerative neuromuscular disease.

Altered beta-tubulin isotype expression in paclitaxel-resistant human prostate carcinoma cells

To investigate the role of beta-tubulin isotype composition in resistance to paclitaxel, an anti-microtubule agent, human prostate carcinoma (DU-145) cells were intermittently exposed to increasing concentrations of paclitaxel. Cells that were selected and maintained at 10 nM paclitaxel (Pac-10) were fivefold resistant to the drug. Pac-10 cells accumulated radiolabelled paclitaxel to the same extent as DU-145 cells and were negative for MDR-1. Analysis of Pac-10 and DU-145 cells by flow cytometry showed similar cell cycle patterns. Immunofluorescent staining revealed an overall increase of alpha- and beta-tubulin levels in Pac-10 cells compared with DU-145 cells. Examination of beta-tubulin isotype composition revealed a significant increase in betaIII isotype in the resistant cells, both by immunofluorescence and by western blot analysis. Reverse transcription-polymerase chain reaction (RT-PCR) analysis of the isotypes confirmed the increase observed for the betaIII by exhibiting ninefold higher betaIII mRNA levels and also showed fivefold increase of the betaIVa transcript. In addition, analysis of paclitaxel-resistant cells that were selected at increasing levels of the drug (Pac 2, 4, 6, 8 and 10) exhibited a positive correlation between increasing betaIII levels and increasing resistance to paclitaxel. Increased expression of specific beta-tubulin isotypes and subsequent incorporation into microtubules may alter cellular microtubule dynamics, providing a defence against the anti-microtubule effects of paclitaxel and other tubulin-binding drugs.

Cloning and sequencing of human betaIII-tubulin cDNA: induction of betaIII isotype in human prostate carcinoma cells by acute exposure to antimicrotubule agents

Antimicrotubule drugs are used as chemotherapeutic agents due to their effects on essential cellular functions such as mitosis, organelle transport and maintenance of cell shape. When used in combination, paclitaxel with estramustine or vinblastine has demonstrated activity against hormone refractory prostate cancer. To understand the mechanism of resistance that develops in patients as a result of antimicrotubule drug therapy, we exposed human prostate carcinoma cells to IC20 and IC40 doses of estramustine, paclitaxel or vinblastine for 48 h and examined the beta-tubulin (the cellular target) isotype composition. The results revealed an increase in the betaIII-tubulin isotype as a result of drug treatment both at protein and message levels. In addition, examination of human brain cell lines with different intrinsic levels of betaIII showed that cell lines with higher betaIII levels were more resistant to paclitaxel. These results are in agreement with our previous findings in human prostate carcinoma cell lines that were made resistant to estramustine or paclitaxel and suggest an important function for betaIII in antimicrotubule drug resistance. Also, the complete coding sequence of human betaIII tubulin reported here will provide molecular tools for future investigations.

Phase II trial of 96-hour paclitaxel plus oral estramustine phosphate in metastatic hormone-refractory prostate cancer

PURPOSE

To evaluate the antitumor activity of 96-hour paclitaxel and daily oral estramustine phosphate (EMP) in patients with metastatic hormone-refractory prostate cancer (HRPC).

PATIENTS AND METHODS

Thirty-four patients with adenocarcinoma of the prostate that progressed after one or more hormonal therapies and a trial of antiandrogen withdrawal were enrolled onto this phase II trial. Patients received paclitaxel 120 mg/m2 by 96-hour intravenous (i.v.) infusion on days 1 through 4 of each 21-day cycle, together with daily oral EMP 600 mg/m2/d, continuously.

RESULTS

Four of nine patients with measurable disease had objective responses (one complete response [CR] and three partial responses [PRs]) in liver (two patients) or nodes (two patients) of 2, 6, 8, and 20 months' duration. Of 25 assessable patients with metastases limited to bone, 14 had a > or = 50% decline in pretreatment prostate-specific antigen (PSA) level sustained for at least 6 weeks and seven had a > or = 80% decline. Overall, 17 of 32 patients (53.1%) with elevated pretreatment PSA levels had a > or = 50% decline of PSA and nine (28.1%) had a > or = 80% decrease. The main toxicities (> or = grade 2) were nausea, fluid retention, and fatigue, which occurred in 33%, 33%, and 24.2% of patients. Median time to progression, based on increasing PSA level and other clinical criteria, was 22.5 weeks. The estimated median overall survival time is 69 weeks.

CONCLUSION

The combination of EMP and 96-hour paclitaxel is an active regimen for patients with HRPC. These results further support the therapeutic strategy of combining agents that impair microtubule function by complementary mechanisms.

Immunohistochemical analysis of beta-tubulin isotypes in human prostate carcinoma and benign prostatic hypertrophy

BACKGROUND

beta-tubulin, the intracellular target of several antimicrotubule agents, is encoded by at least six genes and exists as multiple isotypes with tissue-specific expression. Previous in vitro studies indicated that tubulin isotype composition may affect polymerization properties, dynamics, and sensitivity to drugs.

METHODS

To investigate the isotype composition of beta-tubulin in human prostate, tissues were collected from 26 patients after radical prostatectomy and sections were stained with isotype-specific antibodies.

RESULTS

beta IV tubulin is the predominant isotype in benign prostatic hyperplasia (BPH) and adenocarcinoma, showing significantly stronger immunohistochemical expression than beta II and beta III, particularly in Gleason's grade 3 and 4 cancers. Staining for the beta II isotype was invariably weak and often absent in BPH and normal glands. There was a marked increase in beta II isotype stain from BPH to cancer in 77% of the patients, suggesting that the expression of this isotype is related to malignant status.

CONCLUSIONS

The beta II tubulin isotype is a potential marker for prostate adenocarcinoma. The possibility that tumor beta-tubulin isotype composition may effect the response to antimicrotubule drug therapy in prostate cancer and other tumors merit investigation.

Phase I trial of fluorouracil modulation by N-phosphonacetyl-L-aspartate and 6-methylmercaptopurine ribonucleoside (MMPR), and leucovorin in patients with advanced cancer

The results of several clinical trials support the hypothesis that biochemical modulation may enhance the antitumor activity of 5-Fluorouracil (5-FU). We have performed a phase I trial using a combination of three different biochemical modulators at the optimal dose established in previous clinical trials. The modulators include: phosphonacetyl-l-aspartate (PALA), which may increase 5-FU incorporation into RNA; leucovorin, which potentiates thymidylate synthase inhibition; and 6-methylmercaptopurine riboside (MMPR), which promotes the intracellular retention of fluorinated nucleotides. The treatment regimen consisted of PALA 250 mg/m2 day 1, followed 24 h later by MMPR 150 mg/m2 as an iv bolus, and the initiation of a 24-hour infusion of 5-FU along with leucovorin 50 mg/m2. This regimen was repeated weekly. Doses of 5-FU were escalated in cohorts of four or more patients from 2,000 to 2,600 mg/m2. Among 20 patients entered, the majority had colorectal cancer, and most had received prior 5-FU treatment. Toxicity was predominantly gastrointestinal, and diarrhea was dose-limiting at a 5-FU dose of 2600 mg/m2. There were three partial remissions observed, two of whom had colorectal cancer. Emerging data that casts doubt on the modulation value of PALA at this dose and schedule suggests that revision of this regimen be considered before Phase II trial.

Increase of beta(III)- and beta(IVa)-tubulin isotopes in human prostate carcinoma cells as a result of estramustine resistance

Estramustine (EM), an antimicrotubule agent, is effective against hormone-refractory prostate cancer when used in combination with vinblastine or paclitaxel. To understand the effect of EM on beta-tubulin, a cellular target for this class of drugs, human prostate carcinoma cells (DU-145) were made resistant to EM, and two cell lines were selected at 12- (EM-12) and 15-microMolar (EM-15) concentrations of the drug. These cell lines exhibited 8- to 9-fold resistance to EM and 2- to 4-fold cross-resistance to paclitaxel. Immunofluorescent staining of the cells with beta-tubulin isotype-specific antibodies showed an approximately 6-fold increase in the beta(III)-tubulin levels and moderate increase in overall beta-tubulin levels in EM-resistant cells when compared to DU-145 cells. This increase of beta(III) isotype was confirmed by Western analysis. A reverse transcriptase-PCR assay was also employed using beta-tubulin isotype-specific primers to quantify beta-tubulin isotype RNA. A 4-fold increase in beta(III) and a 3-fold increase in beta(IV alpha) transcript were seen in both EM-resistant cell lines. These results indicate that overexpression of specific beta-tubulin isotypes may play a role in the cellular defense against EM and other antimicrotubule agents.

Paclitaxel plus estramustine in metastatic hormone-refractory prostate cancer

Combination antimicrotubule therapy with estramustine phosphate (EMP) and vinblastine has reproducible activity in metastatic hormone-refractory prostate cancer (HRPC) with an objective response rate of 31%. Although paclitaxel (Taxol; Bristol-Myers Squibb Company, Princeton, NJ) by 24-hour infusion was inactive in HRPC, 0.5 to 1.0 nmol/L concentrations of paclitaxel combined with EMP exerted synergistic cytotoxicity in DU-145 androgen-independent human prostate cancer cell lines. Based on these results, we treated 24 patients with HRPC using the combination of paclitaxel 120 to 140 mg/m2 by 96-hour intravenous infusion every 3 weeks plus daily oral EMP at 600 mg/m2/d. Of seven patients with measurable soft tissue metastases, three have attained partial responses and a fourth patient is nearing partial response status. Of 16 patients with bone-only disease evaluated by change in serum prostate-specific antigen levels, 11 patients (68.8%) have had decreases of > or = 50% from pretreatment baseline. The prostate-specific antigen decrease has exceeded 80% in six of 16 (37.5%) patients. For all 23 evaluable patients, the prostate-specific antigen has decreased by > or = 50% in 15 (65.2%) and by > or = 80% in eight (34.7%). Grade 4 leukopenia occurred in one of 21 patients treated at the paclitaxel dose of 120 mg/m2/96 hr and one of three patients treated at 140 mg/m2/96 hr. The incidence of nausea (50%) and peripheral edema (37.5%) was similar to that associated with single-agent EMP. These results demonstrate that 96-hour paclitaxel plus EMP is active in HRPC and provide further evidence that the rational combination of antimicrotubule agents leads to synergistic antitumor activity in HRPC.

Phase I study of paclitaxel and estramustine: preliminary activity in hormone-refractory prostate cancer

Estramustine phosphate is a unique antimitotic agent that binds to tubulin and microtubule-associated proteins. Preclinically, estramustine combined with other microtubule inhibitors, like vinblastine or paclitaxel (Taxol; Bristol-Myers Squibb Company, Princeton, NJ), produced additive or greater antimitotic and cytotoxic effects. Clinically, the estramustine/vinblastine combination has significant activity in hormone-refractory prostate cancer. We have begun a phase I study of paclitaxel by 96-hour continuous infusion every 3 weeks combined with daily oral estramustine (600 mg/m2). Eighteen patients with refractory solid tumors have received paclitaxel doses ranging from 80 to 140 mg/m2. Grade 3 or 4 granulocytopenia occurred in one of seven and two of four patients treated at the 120- and 140-mg/m2 dose levels, respectively. The latter two patients experienced grade 3 mucositis and had mean plasma paclitaxel levels exceeding 0.1 mumol/L. Other toxicities, principally nausea and hepatic function abnormalities, have been mild. The apparent steady-state concentrations of paclitaxel 100 and 120 mg/m2 administered with estramustine are similar to those reported for single-agent paclitaxel administered as a 96-hour infusion at doses of 100 and 120 mg/m2. In contrast, at the 140 mg/m2 dose level, paclitaxel concentrations increased throughout the infusion, and steady state was not reached in three of the four patients treated. Objective responses have been observed in two of three patients with adenocarcinoma of the esophagus and in two patients with hormone-resistant prostate cancer and measurable soft tissue metastases. Two additional patients with prostate cancer have been treated with the estramustine/paclitaxel combination, one achieving a major response and the other stable disease. The recommended phase II dose for 96-hour infusional paclitaxel with daily oral estramustine is at least 120 mg/m2. Studies to determine the effect of estramustine on paclitaxel pharmacokinetics are continuing. The antitumor activity observed merits phase II studies of this combination in hormone-resistant prostate cancer and other malignancies.

Modulation of P-glycoprotein activity by estramustine is limited by binding to plasma proteins

BACKGROUND

Estramustine previously has been shown to interact with P-glycoprotein and to restore intracellular accumulation of vinblastine and paclitaxel in cells overexpressing this drug transporter. However, the ability of estramustine to potentiate the cytotoxicities of several drugs was less than that expected. To resolve this apparent discordance, the authors examined the effects of serum on the actions of estramustine.

METHODS

The cytotoxicities of anticancer drugs with or without estramustine or verapamil toward MCF-7 breast carcinoma cells and a P-glycoprotein-overexpressing subline MCF-7/ADR were determined using the sulforhodamine-binding assay. The extent of intracellular accumulation of [3H]vinblastine and [3H]paclitaxel was determined for each using standard methods, and the binding of radiolabeled drugs to plasma proteins was characterized by equilibrium dialysis.

RESULTS

Without serum, the sensitivities of MCF-7/ADR cells to several P-glycoprotein-transported drugs were increased by estramustine and verapamil. Conversely, when the cells were treated with a 10% serum, the cytotoxicities of these drugs were increased by verapamil, but not by estramustine. Without serum, intracellular accumulation of [3H]vinblastine and [3H]paclitaxel by MCF-7/ADR cells was increased markedly by verapamil and estramustine; however, serum suppressed the effects of estramustine much more strongly than those of verapamil. Equilibrium dialysis experiments demonstrated that [3H]estramustine binds to plasma proteins, predominantly albumin, whereas [3H]paclitaxel binds to albumin and alpha 1-acid-glycoprotein, and [3H]vinblastine binds predominantly to alpha 1-acid-glycoprotein.

CONCLUSION

Although estramustine can bind to P-glycoprotein, its effectiveness as a reversing agent in vivo likely is limited by binding to plasma proteins.

Phase I trial of fluorouracil modulation by N-phosphonacetyl-L-aspartate and 6-methylmercaptopurine ribonucleoside

Inhibition of pyrimidine and purine synthesis has been demonstrated to potentiate 5-fluorouracil (5-FU) activity in preclinical models. Low-dose phosphonacetyl-L-aspartate (PALA) potentiates the incorporation of 5-FU into RNA, without detectably increasing its toxicity. 6-Methylmercaptopurine riboside (MMPR) results in inhibition of purine biosynthesis with elevation of phosphoribosyl pyrophosphate (PRPP), which in turn is believed to increase the phosphorylation and intracellular retention of 5-FU. We conducted a phase I clinical trial to determine the maximum tolerated dose of 5-FU in combination with low-dose PALA and a biochemically-optimized dose of MMPR. The regimen consisted of PALA 250 mg/m2 given on day 1, followed 24 h later by MMPR 150 mg/m2, and escalating doses of 5-FU from 1625 to 2600 mg/m2 by 24 h continuous infusion. This regimen was repeated weekly. A group of 29 patients with a diagnosis of malignant solid tumor were entered; their median performance status was 1. The dose-limiting toxicity was mucositis, while other gastrointestinal toxicity was minimal. Two patients also experienced ischemic chest pain during the 5-FU infusion. The maximum tolerated dose of 5-FU in this combination was 2600 mg/m2. Several responses were observed including a complete remission in a previously treated breast cancer patient and two partial responses in breast and colon cancer. MMPR pharmacokinetics were obtained from urine analyses in 21 patients on this trial; there was no correlation between the pharmacokinetics of MMPR and the toxicity observed. This regimen was well tolerated and phase II trials are warranted using PALA 250 mg/m2, MMPR 150 mg/m2, and 5-FU 2300 mg/m2 by continuous infusion over 24 h.

Phase I study of phosphonacetyl-L-aspartate, 5-fluorouracil, and leucovorin in patients with advanced cancer

Low-dose phosphonacetyl-L-aspartate (PALA) may potentiate both 5-fluorouracil (5-FU) incorporation into RNA and thymidylate synthase inhibition by 5-fluorodeoxyuridylate (5-FdUMP). The gastrointestinal toxicity of 5-FU is not increased by PALA administration. Exogenous leucovorin, on the other hand, which enhances thymidylate synthase inhibition, appears to increase the clinical toxicity of 5-FU in a dose-dependent manner. As a result, the clinical use of high-dose leucovorin requires a marked dose reduction of 5-FU. Extracellular leucovorin levels of 1 microM suffice to maximize the enhancement of thymidylate synthase inhibition in several models. We conducted a trial to add leucovorin to the PALA/5-FU regimen. We chose a leucovorin dose that was predicted to yield end-infusion total reduced folate concentrations of 1 microM. The major endpoint was to determine the maximum tolerated dose of 5-FU in this combination. The regimen consisted of 250 mg/m2 PALA given on day 1 and, 24 h later, escalating 5-FU doses ranging from 1,850 to 2,600 mg/m2 admixed with 50 mg/m2 leucovorin and given by 24-h infusion. Courses were repeated weekly. A total of 24 patients with a median performance status of 1 were entered at three dose levels. Diarrhea was dose-limiting; 6/13 patients had grade II or worse diarrhea at 2,600 mg/m2. Dose modification resulted in a mean dose intensity of 2,300 mg/m2 at both the 2,600- and 2,300-mg/m2 dose levels. The 2,300-mg/m2 dose is suitable for phase II testing of this regimen. Three patients (two with breast cancer and 1 with sarcoma) had a partial remission. We measured steady-state concentrations (Css) of 5-FU in 23 patients. The mean Css increased with dose from 0.738 to 1.03 micrograms/ml. Total body clearance did not vary with dose in this range. Patients with grade II or worse diarrhea had a higher mean Css (1.10 +/- 0.19) than those with grade O or I toxicity (0.835 +/- 0.25, P < 0.02). Total bioactive folates (bound and free) were measured using a biological assay. Pretreatment values ranged from 2 to 52 nM and were not predictive of toxicity. End-infusion (23-h) values were somewhat lower than predicted and ranged from 400 to 950 nM. The risk of diarrhea was positively correlated with end-infusion total folate values. In a logistic regression analysis, total folate values obtained at 23 h were a more powerful predictor of diarrhea than were 5-FU Css values.(ABSTRACT TRUNCATED AT 400 WORDS)

Phase II study of topotecan in metastatic hormone-refractory prostate cancer

Systemic chemotherapy with currently available agents has not improved survival for patients with hormone refractory prostate cancer (HRPC), consequently, the evaluation of new agents is warranted. Topotecan is a specific inhibitor of topoisomerase I with broad antitumor activity in preclinical studies. The purpose of this phase II trial was to determine the objective response rate of topotecan administered as a 30 minute infusion for five consecutive days in men with metastatic HRPC. Thirty-four evaluable patients were treated with topotecan 1.1-1.5 mg/m2 as a 30 minute infusion daily for five days, repeated every three weeks until disease progression or unacceptable toxicity. Response was assessed with a combination of standard solid tumor response criteria and the serum prostate specific antigen (PSA) for patients with bidimensionally measurable disease, and by serial measurements of the PSA in patients with bone only (evaluable) disease. One of 13 patients (7.6%) with measurable soft tissue disease had a PR in nodal sites. Of 21 patients with only osseous metastases, 1 (4.7%) had improvement in bone scan. Six of the 34 evaluable patients (17.6%) had the serum PSA decrease by > or = 50% and 2 (5.8%) had PSA decreases of > or = 75%. Toxicity was chiefly hematologic with 66% of patients experiencing Grade 3 or 4 granulocytopenia. Thirty-nine percent of cycles required a delay to allow for hematologic recovery and ten patients required red cell transfusions. Non-hematologic toxicity, mainly nausea and alopecia, was mild. Topotecan administered at this dose and schedule has limited activity in patients with HRPC. Further trials of topo I inhibition in HRPC should utilize alternative schedules of topotecan (e.g., prolonged infusion) or other camptothecin analogs with more potent topo I inhibitory activity.

Significant activity of paclitaxel in advanced transitional-cell carcinoma of the urothelium: a phase II trial of the Eastern Cooperative Oncology Group

PURPOSE

To assess the efficacy and toxicity of single-agent paclitaxel as first-line chemotherapy in patients with locally advanced or metastatic transitional-cell carcinoma of the urothelium.

PATIENTS AND METHODS

Twenty-six eligible patients were enrolled onto this cooperative group study and treated with paclitaxel at a dosage of 250 mg/m2 by 24-hour continuous infusion every 21 days until progression or patient intolerance. All patients received recombinant human granulocyte colony-stimulating factor (rhG-CSF) at 5 micrograms/kg/d for at least 10 days during each cycle.

RESULTS

Eleven of 26 patients (42%; 95% confidence interval [CI], 23% to 63%) demonstrated an objective response, with seven achieving a complete clinical response (CR) (27%; 95% CI, 12% to 48%) and four (15%) a partial response (PR). The median duration of response in the 11 responders is 7+ months (range, 4 to 17), with five responders (four CRs, one PR) remaining progression-free at 5, 6, 10, 12, and 16 months from the start of therapy. The estimated median survival duration for all patients is 8.4 months. Hematologic toxicity consisted of anemia (12% grade 3) and granulocytopenia (4% grade 3, 19% grade 4), with two patients developing granulocytopenic fevers. Nonhematologic toxicity included grade 3 mucositis in 11%, grade 3 neuropathy in 11%, and grade 4 diarrhea in 4%.

CONCLUSION

Single-agent paclitaxel at this dosage and schedule is one of the most active single agents in previously untreated patients with advanced urothelial carcinoma, and is well tolerated by this patient population when given with hematopoetic growth factor support.

P-glycoprotein binding and modulation of the multidrug-resistant phenotype by estramustine

BACKGROUND

Previous preclinical studies of combinations of estramustine and vinblastine or paclitaxel (Taxol) have shown that it is possible to achieve a greater than additive cytotoxicity with these antimicrotubule drug combinations. Phase II studies in hormone-refractory prostate cancer have demonstrated clinical antitumor activity of sufficient magnitude to stimulate further laboratory and clinical studies of these drugs combinations.

PURPOSE

Our purpose was to characterize the interactions of estramustine with P-glycoprotein and to determine its effects.

METHODS

Standard laboratory techniques were used to study the effects of estramustine on intracellular drug concentrations, cytotoxicity, and induction of messenger RNA (mRNA) for the MDR1 (also known as PGY1) gene. Using a photoaffinity analogue of estramustine 17-0-[[2-[3-(4-azido-3-[125I]-iodophenyl) propionamido]ethyl]-carbamyl]estradiol-3-N-bis(2-chloroethyl)ca rba mate ([125I]AIPP-estramustine), binding to the membrane proteins of human ovarian (SKOV3) and their multidrug-resistant counterpart SKVLB1 cells was studied. Southern-blot analysis was performed on DNA extracted from human prostate carcinoma wild-type DU145, estramustine-resistant cell line (E4), and SKVLB1 cells.

RESULTS

Membrane fractions from SKOV3 and SKVLB1 cells were analyzed for proteins that could be photoaffinity labeled with [125I]AIPP-estramustine. Competitive inhibition of this binding was achieved with excess concentrations of (in order of efficacy) estramustine, vinblastine, verapamil, progesterone, and to a lesser degree, by paclitaxel but not with estramustine phosphate, estradiol, and estriol. SKVLB1 cells accumulated much less [3H]vinblastine and [3H]paclitaxel than did SKOV3 cells. Estramustine caused a concentration-dependent enhancement of drug accumulation in the SKVLB1 cells to a maximum of approximately 12-fold. No effect of estramustine was apparent for the wild-type SKOV3 cells. In comparison with verapamil, estramustine was less effective as a modulator; however estramustine demonstrated good chemosensitizing activity in combination with actinomycin D and vinblastine. Neither short-term, low-dose no longer-term, higher concentration were found to produce measurable transcript (mRNA for the MDR1 gene levels. Such data suggest that, at least levels. Such data suggest that, at least for two distinct human cell line (SKOV3 and DU145), estramustine does not induce the overexpression of the MDR1 gene.

CONCLUSION

It is apparent from the P-glycoprotein data that estramustine interacts with this efflux pump, altering intracellular drug accumulation. Overall, the nonempiric basis for including estramustine in clinical protocols that contain other multidrug-resistant drugs is strengthened by the present data.

Phase I/pharmacokinetic study of topotecan by 24-hour continuous infusion weekly

Topotecan (SK&F 104864, hycamptamine, NSC 609699) is believed to exert its cytotoxic effects through inhibition of topoisomerase I, the activity of which recovers rapidly on removal of the drug in vitro. In vivo studies show that the activity of topotecan is schedule dependent, favoring repeated doses. Early human studies showed that topotecan (the active lactone) had a short half-life in plasma. To prolong drug exposure, we administered topotecan as a 24-h i.v. infusion and repeated it weekly. We treated 32 patients with doses of 1.0-2.0 mg/m2. Median performance status was 1, and all but four patients had received prior chemotherapy. Dose-limiting neutropenia occurred at doses > or = 1.75 mg/m2; nadirs were observed after 1-3 doses. The recommended phase II dose is 1.5 mg/m2/week. One patient with metastatic colon cancer had a partial response. Both plasma topotecan (lactone) and total topotecan (measured by converting the hydroxyacid form to the lactone by acidification of the sample) were measured by high-performance liquid chromatography in 21 patients. During infusion, mean topotecan plasma steady-state concentrations ranged from 4.7-11.4 nM. Plasma elimination was best fit to a one-compartment model with a mean t1/2 of 3.5 h. The mean total body clearance was 388 ml/min/m2. Concentrations of the inactive form approximated those of the lactone throughout. No evidence for dose-dependent pharmacokinetics was observed in this dose range. Pharmacodynamic analysis, using the sigmoid Emax model, revealed that the pharmacokinetic parameters of both lactone and total drug were positively correlated with bone marrow toxicity. Total drug steady-state plasma concentration provided a good estimate of neutropenia, suggesting a simple, easily monitored, pharmacokinetic parameter for adaptive dosing using this schedule. Phase II evaluation of this weekly schedule is indicated in solid tumors.