Unpredicted clinical pharmacology of UCN-01 caused by specific binding to human alpha1-acid glycoprotein

The pharmacokinetics of UCN-01 after administration as a 72- or 3-h infusion to cancer patients in initial Phase I trials displayed distinctive features that could not have been predicted from preclinical data. The distribution volumes (0.0796-0.158 liters/kg) and the systemic clearance (0.0407-0.252 ml/h/kg) were extremely low, in contrast to large distribution volume and rapid systemic clearance in experimental animals. The elimination half-lives (253-1660 h) were unusually long. In vitro protein binding experiments demonstrated that UCN-01 was strongly bound to human alpha1-acid glycoprotein. The results suggest that unusual pharmacokinetics of UCN-01 in humans could be due, at least in part, to its specifically high binding to alpha1-acid glycoprotein.

A phase II study of bromocriptine in patients with androgen-independent prostate cancer

Prolactin is an important physiological regulator of prostate development and growth in preclinical models. In prostate cancer there is strong evidence that prolactin exerts a trophic effect independent of testosterone. In addition, patients with prostate cancer that have an elevated prolactin level correlated with a poorer prognosis. Based on these data, we evaluated the clinical effect of prolactin suppression using bromocriptine in patients with androgen-independent prostate cancer. We conducted an open-label phase II trial of bromocriptine in patients with progressive metastatic prostate cancer. Basal and thyrotropin releasing hormone (TRH)-stimulated prolactin levels were utilized as biological endpoints for determining the dose of bromocriptine. All patients continued to receive complete androgen blockade. Thirteen patients were enrolled (median age 69.5 years). There were no complete or partial responses associated with bromocriptine in 11 of the evaluable patients. The mean duration of bromocriptine treatment was 8.2 weeks (2-14 weeks). One patient had a clinically insignificant decrease in prostate-specific antigen (PSA) and another patient had a 19.9% decrease in PSA with progression of a soft tissue mass. The vast majority of patients (10 of 11) had suppression of prolactin with a bromocriptine dose of 2.5 mg three times a day. One patient required a dose adjustment due to inadequate suppression, with a final maintenance dose of bromocriptine 12.5 mg per day resulting in complete suppression. No serious treatment-related toxicities were observed. The most common complications noted were nausea, headaches, dizziness, and fatigue. Our data showed that 2.5 mg three times per day of bromocriptine suppressed prolactin in 90% of the patients. Furthermore, this dose appears to be well tolerated.

Inhibition of angiogenesis by thalidomide requires metabolic activation, which is species-dependent

Thalidomide has been shown to be an inhibitor of angiogenesis in a rabbit cornea micropocket model; however, it has failed to demonstrate this activity in other models. These results suggest that the anti-angiogenic effects of thalidomide may only be observed following metabolic activation of the compound. This activation process may be species specific, similar to the teratogenic properties associated with thalidomide. Using a rat aorta model and human aortic endothelial cells, we co-incubated thalidomide in the presence of either human, rabbit, or rat liver microsomes. These experiments demonstrated that thalidomide inhibited microvessel formation from rat aortas and slowed human aortic endothelial cell proliferation in the presence of human or rabbit microsomes, but not in the presence of rat microsomes. In the absence of microsomes, thalidomide had no effect on either microvessel formation or cell proliferation, thus demonstrating that a metabolite of thalidomide is responsible for its anti-angiogenic effects and that this metabolite can be formed in both humans and rabbits, but not in rodents.

Phase II trial with dose titration of paclitaxel for the therapy of human immunodeficiency virus-associated Kaposi's sarcoma

PURPOSE

To investigate the antitumor activity and safety of paclitaxel in patients with advanced human immunodeficiency virus (HIV)-associated Kaposi's sarcoma (KS).

PATIENTS AND METHODS

Twenty-nine patients with advanced HIV-associated KS were enrolled. The patients were overall quite immunosuppressed (median CD4 count, 15 cells/microL). Paclitaxel was initially administered at 135 mg/m2 over 3 hours every 3 weeks without filgrastim support; the dose was increased as tolerated to a maximum of 175 mg/m2. Patients who failed to respond or progressed could then receive filgrastim support or paclitaxel administered over 96 hours.

RESULTS

Of 28 assessable patients, 20 had major responses (18 partial responses [PRs], one clinical complete response [CR], and one CR), for a major response rate of 71.4% (95% confidence interval [CI], 51.3% to 86.8%). Each of the five patients with pulmonary KS responded, as did all four assessable patients who had previously received anthracycline therapy for KS. Of six patients who went on to receive a 96-hour infusion of paclitaxel, five had major responses. Neutropenia was the most frequent dose-limiting toxicity; possible novel toxicities included late fevers, late rash, and eosinophilia. Two patients developed an elevated creatinine concentration and one cardiomyopathy.

CONCLUSION

Paclitaxel has substantial activity against advanced HIV-associated KS as a single agent, even in patients with pulmonary involvement or who had previously received anthracyclines. Further research is needed to define the optimal treatment schedule and its role vis-a-vis the other available therapies for this disease.

Elevated carcinoembryonic antigen in patients with androgen-independent prostate cancer

BACKGROUND

Extraordinarily high serum carcinoembryonic antigen (CEA) values have been reported to be associated with many malignant disorders, including carcinoma with primary sites in the colon, pancreas, stomach, bile duct, lung, and breast. This study was undertaken to determine if a marked elevation of serum CEA levels in androgen-independent prostate cancer patients exists, and to evaluate the potential of using CEA monitoring as a marker for disease progression.

METHODS

Records from 141 patients with progressive androgen-independent prostate cancer who were treated at the National Cancer Institute from 1990 to 1996 were analyzed. Serum CEA concentrations were measured using a micro-particle enzyme immunoassay.

RESULTS

Among these cases of prostatic carcinoma, 69 (48.9%) had abnormally elevated plasma CEA values (greater than the normal upper limit of 2.5 ng/mL) at some time during their treatment on a clinical investigation protocol. No correlation was found between the elevated CEA concentrations and prostate specific antigen (PSA). In comparison, 32.5% of patients with elevated CEAs had disease that had metastasized to soft tissue (adenopathy, etc) versus 22.2% with normal CEA who had soft tissue involvement (p = 0.3 X2). We examined the CEA values with respect to survival time, defined as the interval from the date of the earliest CEA level to the date of death and found no association (p > 0.3).

CONCLUSIONS

Based on these observations, it appears that in the context of androgen-independent prostate cancer, CEA can be elevated but is an inviable surrogate marker of disease progression with minimal prognostic value.

Phase II study of suramin plus aminoglutethimide in two cohorts of patients with androgen-independent prostate cancer: simultaneous antiandrogen withdrawal and prior antiandrogen withdrawal

Management of prostate cancer progression after failure of initial hormonal therapy is controversial. Recently, the activity of the simple discontinuation of antiandrogen therapy has been established by several groups, as well as the enhanced activity when combined with adrenal suppression (i.e., aminoglutethimide and hydrocortisone). Furthermore, suramin has generated considerable interest following reports of response rates ranging from 17 to 70%. More recently, suramin response rates of 18 and 22% have been reported when the potential confounding variables of flutamide withdrawal and hydrocortisone were prospectively controlled. On the basis of the activity of combining aminoglutethimide with flutamide withdrawal, we designed a protocol in which suramin was combined with aminoglutethimide in two cohorts of patients (those with simultaneous antiandrogen withdrawal compared to those who had previously discontinued antiandrogen therapy). Eighty-one evaluable patients were enrolled in this study between June 1992 and November 1994. Patients were a priori divided into two cohorts, those receiving prior antiandrogen withdrawal (n = 56) and those receiving simultaneous antiandrogen withdrawal (n = 25) at the time the patients were enrolled into the trial. For the group that discontinued antiandrogen prior to enrolling in therapy, the partial response rate (> 50% decline in PSA for > 4 weeks) was 14.2%, whereas the partial response was 44% for those patients who discontinued their antiandrogen at the time of starting suramin and aminoglutethimide. The median time to progression was 3.9 months in patients failing prior antiandrogen withdrawal and 5.5 months in those patients having concomitant antiandrogen withdrawal (P = 0.36 for the overall difference). The progression-free survival estimate at 1 year for patients having prior antiandrogen withdrawal was 19.8% [95% confidence interval (CI), 11-32.9%]. For those patients who experienced antiandrogen withdrawal simultaneous with the treatment, the progression-free survival estimates at 1 and 2 years were 27.1 (95% CI, 13.2-47.6%) and 4.5% (95% CI, 0.8-21.6%). The median survival time for those patients having prior antiandrogen withdrawal was 14.2 months, whereas the median survival was 21.9 months for those having concomitant antiandrogen withdrawal (P = 0.029 for the overall difference). In conclusion, the partial response rate of 44% for those who had concomitant flutamide withdrawal with adrenal suppression was consistent with that of other reports using a similar maneuver. Although this study was not randomized and thus we should not over-interpret the results, flutamide withdrawal plus adrenal suppression appears to have greater activity than flutamide withdrawal alone. Furthermore, these data suggest that suramin adds little to the response rate observed for other adrenal suppressive agents in the presence of antiandrogen withdrawal. This interpretation is in agreement with those studies controlling for adrenal suppression and flutamide withdrawal prior to suramin administration, which noted modest activity of short duration. Given that antiandrogen withdrawal is now accepted as an active maneuver for a subset of patients progressing after maximum androgen blockade, we propose that future trials attempting to maximize response rates incorporate this maneuver whenever possible into prospectively designed regimens.

Single-dose pharmacokinetics of thalidomide in human immunodeficiency virus-infected patients

The pharmacokinetics of thalidomide in nine human immunodeficiency virus-infected patients were studied. Single doses of thalidomide were well absorbed, with mean peak concentrations (+/- standard deviations) of 1.17 +/- 0.21 and 3.47 +/- 1.14 microg/ml in the 100- and 300-mg dosing groups, respectively, and the mean elimination half-life was approximately 6 h. Adverse effects were mild, with drowsiness being reported for seven of nine patients.

Similar clinical outcomes in African-American and non-African-American males treated with suramin for metastatic prostate cancer

African-American males have a higher incidence of prostate cancer than non-African-American males and an overall poorer prognosis. Environmental factors such as socioeconomic status and biological factors such as an increased frequency of androgen receptor mutation have been identified as causal. As androgen ablation therapy is ubiquitous in the treatment of metastatic prostate cancer, little information is available on clinical outcome independent of hormone therapy. Our experience at the Warren G. Magnusson Clinical Center, National Institutes of Health with the anticancer agent, suramin, offers the opportunity to study clinical outcome in patients treated with an agent whose tumoricidal activity is not dependent on androgen receptor function. Clinical outcome was examined retrospectively in 43 patients treated on a single suramin-based protocol and evaluated as a function of ethnic background. No significant difference in time to disease progression or survival was observed between African Americans (n = 4) and the other 39 patients. These findings are consistent with the hypothesis that therapies that work through mechanisms independent of the androgen receptor may result in similar outcomes across ethnic groups.

Safety, tolerance, and pharmacokinetics of amphotericin B lipid complex in children with hepatosplenic candidiasis

The safety, tolerance, and pharmacokinetics of amphotericin B lipid complex (ABLC) were studied in a cohort of pediatric cancer patients. Six children with hepatosplenic candidiasis (HSC) received 2.5 mg of ABLC/kg of body weight/day for 6 weeks for a total dosage of 105 mg/kg. Mean serum creatinine (0.85 +/- 0.12 mg/dl at baseline) was stable at the end of therapy at 0.85 +/- 0.18 mg/dl and at 1-month follow-up at 0.72 +/- 0.12 mg/dl. There was no increase in hepatic transaminases. Mean plasma concentrations over the dosing interval (C(ave)) and area under the curve from 0 to 24 h (AUC(0-24h)) increased between the first and seventh doses but were similar between doses 7 and 42, suggesting that steady state was achieved by day 7 of therapy. Following the final (42nd) dose of ABLC, mean AUC(0-24h) was 11.9 +/- 2.6 microg h/ml, C(ave) was 0.50 +/- 0.11 microg/ml, maximum concentration of the drug in whole blood was 1.69 +/- 0.75 microg/ml, and clearance was 3.64 +/- 0.78 ml/min/kg. Response of hepatic and splenic lesions was monitored by serial computerized tomographic and magnetic resonance imaging scans. The five evaluable patients responded to ABLC with complete or partial resolution of physical findings and of lesions of HSC. During the course of ABLC infusions and follow-up, there was no progression of HSC, breakthrough fungemia, or posttherapy recurrence. Hepatic lesions continued to resolve after the completion of administration of ABLC. Thus, ABLC administered in multiple doses to children was safe, was characterized by a steady state attainable within 1 week of therapy, and was effective in treatment of HSC.

Flutamide withdrawal plus hydrocortisone resulted in clinical complete response in a patient with prostate carcinoma

BACKGROUND

Combined androgen blockade (CAB) (medical or surgical castration plus antiandrogen therapy) is considered by many to be the optimal endocrine maneuver for patients with metastatic prostate carcinoma. When progression occurs after CAB, the discontinuation of the antiandrogen is recommended. The authors present a patient that had a clinical complete response to flutamide withdrawal plus hydrocortisone that, at last follow-up, had been maintained for more than 46 months.

METHODS

A 71-year-old man with a positive family history of prostate carcinoma presented in 1989 with urinary frequency and a suspicious digital rectal examination. He was found to have a poorly differentiated adenocarcinoma (Gleason 4+4). He was started on CAB and his prostate specific antigen (PSA) concentration declined from 96 ng/mL to the normal range and was maintained for the next 24 months. In 1991 his PSA began to rise, and reached 64 ng/mL by 1993. The patient was enrolled on a clinical trial that discontinued the flutamide administration and hydrocortisone was initiated.

RESULTS

Physical examination at the time of enrollment was unremarkable. His PSA declined to below the limits of detection after this maneuver and at last follow-up had been maintained there for more than 46 months. In 1995, the patient underwent a repeat biopsy of the prostate and all six tissue cores were negative for carcinoma. At last follow-up in December 1996, the patient had no evidence of disease and was being followed routinely; however, the authors were continuing treatment with testicular suppression (leuprolide) plus hydrocortisone.

CONCLUSIONS

The authors believe the residual androgens and steroids produced by the adrenal cortex play a meaningful role in prostate carcinoma cell proliferation. Based on this case and data from trials supporting the activity of flutamide withdrawal plus adrenal suppression, it appears reasonable to evaluate prospectively the discontinuation of antiandrogen versus antiandrogen withdrawal plus adrenal suppression in individuals failing CAB.

Pharmacokinetic studies with recombinant cytokines. Scientific issues and practical considerations

Advances in molecular biology and recombinant DNA technology have led to the development of cytokines as therapeutic agents for a variety of disease states. The pharmacokinetic analysis of cytokines involves the understanding of analytical methods capable of detecting these agents in biological fluids and recognition of several factors which may have an impact on the cytokine concentration-time curves. Enzyme-linked immunosorbent assays (ELISA) have become the most common method of detection and commercial kits are available for a wide variety of cytokines. Monoclonal antibody products are sensitive, have minimal cross-reactivity and are relatively inexpensive when compared with high performance liquid chromatography (HPLC). However, the primary limitation of these assays is their inability to measure biologically active protein. Conversely, bioassays do measure a biological event (i.e. proliferation or cytotoxicity) but are generally not used for cytokine analysis because of their high cost, long assay completion time, lack of specificity, poor sensitivity and influence of environmental conditions on the outcome. The pharmacokinetic profile of recombinant cytokines is influenced by a number of variables: endogenous production, circulating soluble receptors and cell-associated receptors, immunocompetence and antibody production against the cytokine all may influence the disposition of the agent. Thus, pharmacokinetic modelling of cytokines may involve complex models capable of characterising these nonlinear processes and resulting effects. The route of administration is an important variable since cytokines administered by subcutaneous injection may be partially metabolised by proteases present in the subcutaneous tissue. Other methods to simplify cytokine delivery are being actively investigated and include formulations for inhalation, topical and oral administration. A variety of cytokines (including interferon-alpha, interleukin-6 and tumour necrosis factor) are capable of inhibiting cytochrome P450 hepatic enzymes and, therefore, possess the potential to cause drug-cytokine interactions. Inhibition has been demonstrated in several in vitro systems and animal models, although clinical data are currently limited. An increased understanding of the many factors which can alter the analysis and pharmacokinetics of cytokines is essential to the design of optimal dosage regimens.

Continuous hyperthermic peritoneal perfusion with cisplatin for the treatment of peritoneal mesothelioma

PURPOSE

Peritoneal mesothelioma remains a difficult therapeutic challenge. Aggressive debulking combined with continuous hyperthermic peritoneal perfusion (CHPP) using cisplatin (CDDP) is a novel strategy for the treatment of peritoneal mesothelioma, allowing high regional delivery of chemotherapeutics and hyperthermia while minimizing systemic toxicity.

PATIENTS AND METHODS

From June 1993 to May 1996, 10 patients with peritoneal mesothelioma (six men, four women; mean age 40 years, range 15-57) underwent tumor debulking followed by a 90-minute CHPP. CHPP parameters included mean initial CDDP of 120 micrograms/mL (range 81-166), perfusate volume 5.2 L (range 4-7), flow 1.5 L/min, intraperitoneal temperature at three locations-41.5 degrees C, 40.5 degrees C, 41.1 degrees C, and core temperature 38.4 degrees C (range 37.2 degrees C-39.5 degrees C). Nine of 10 patients had malignant peritoneal mesothelioma, eight with associated ascites, while the tenth had a symptomatic, multiply recurrent benign peritoneal mesothelioma. Nine of 10 patients were optimally debulked. Pharmacokinetics were performed on blood and perfusate samples on nine patients; CDDP levels were quantitated by atomic absorption spectroscopy.

RESULTS

Total perfusate cisplatin AUC was a mean of 21-fold higher (range 2- to 116-fold) than total serum cisplatin AUC, and serum CDDP behaved similarly to systemically administered CDDP. Median follow-up after CHPP is 10 months (range 2-32), with no treatment-related mortality. In eight optimally debulked patients there is no evidence of recurrent disease clinically or by CT or MRI. Seven patients with symptomatic ascites have been completely palliated.

CONCLUSIONS

CHPP with CDDP is well tolerated with no significant regional toxicity. Because favorable CDDP pharmacokinetics suggest the potential for enhanced CDDP tumoricidal effect during CHPP, tumor debulking and CHPP may represent an effective strategy for the treatment of peritoneal mesothelioma.

Pharmacometric analysis of the effect of furosemide on suramin pharmacokinetics

STUDY OBJECTIVE

To characterize the effects of furosemide on the pharmacokinetics of suramin, a renally eliminated investigational antineoplastic agent.

DESIGN

Retrospective population pharmacokinetic analysis.

SETTING

Government biomedical research facility.

PATIENTS

Twenty-six men with hormone-refractory prostate cancer and one with adrenocortical carcinoma.

INTERVENTIONS

Patients received suramin by continuous or intermittent infusion with and without concomitant furosemide.

MEASUREMENTS AND MAIN RESULTS

Optimum suramin regimens were achieved by adaptive feedback control, and pharmacokinetic data were collected both in the presence and absence of furosemide. Suramin concentrations were determined by high-performance liquid chromatography (coefficient of variation < 8%). Suramin concentrations were fit to a three-compartment linear model with six coefficients and two rate inputs, which allowed furosemide to affect suramin pharmacokinetics. Individual and population parameter estimates were determined using the iterative two-stage approach. Concomitant furosemide was associated with a median decrease in total body clearance of suramin by 36% (range 0-63%, p < 0.0001). No other parameter was significantly altered, and there was no trend for change in any pharmacokinetic value with time. Suramin plasma concentrations were simulated with and without prolonged furosemide therapy in 26 patients for 12 weeks. The average suramin concentration increased by greater than 33% in 12 patients; 2 patients had a greater than 67% increase in this extreme case model.

CONCLUSION

Coadministration of furosemide with suramin can cause an increase in suramin concentrations; however, due to suramin's long half-life, its rate of accumulation is very slow. Nonetheless, in individuals receiving suramin by nonadaptive control, appropriate precautions should be taken when prolonged furosemide therapy is begun.

Phase I trial of micronized formulation carboxyamidotriazole in patients with refractory solid tumors: pharmacokinetics, clinical outcome, and comparison of formulations

PURPOSE

Cytostatic agents targeted against angiogenesis and tumor cell invasive potential form a new class of investigational drugs. Orally administered carboxyamidotriazole (CAI) (NSC609974) is both antiangiogenic and antimetastatic. An encapsulated micronized powder formulation has been developed to optimize CAI administration. A phase I dose escalation trial with pharmacokinetic analysis has been performed.

PATIENTS AND METHODS

Twenty-one patients with refractory solid tumors and good end organ function and performance status were enrolled onto the study. Patients received a test dose followed 1 week later by daily administration of CAI in the encapsulated micronized formulation at doses of 100 to 350 mg/m2. Patients remained on CAI until disease progression or dose-limiting toxicity. Plasma samples were taken to characterize the pharmacokinetic parameters of this formulation of CAI.

RESULTS

All patients were assessable for toxicity and 18 were assessable for pharmacokinetics and response analysis. Grade 1 and 2 gastrointestinal side effects were observed in up to 50% of patients. Dose-limiting toxicity was observed in both patients treated at 350 mg/m2/d, consisting of reversible grade 2 to 3 cerebellar ataxia (n = 1) and confusion (n = 1). One minor response (MR) was observed in a patient with renal cell carcinoma and another nine patients had disease stabilization (MR + SD = 47%). Pharmacokinetic analysis demonstrated reduced bioavailability (58% reduction) compared with the PEG-400 liquid formulation previously reported.

CONCLUSION

The better toxicity profile of encapsulated micronized CAI with similar frequency of disease stabilization and ease of administration compared with the liquid or gelatin capsule, suggests that the micronized formulation is a preferable formulation for subsequent studies. A dose of 300 mg/m2/d is proposed for phase II investigations.

Pharmacokinetics of elemental platinum (ultrafiltrate and total) after a thirty minute intravenous infusion of ormaplatin

Preclinical data suggest that ormaplatin (tetrachloro-(dl-trans)-1, 2-diamminocyclohexaneplatinum) has substantial activity in cisplatin-resistant tumor models and may be less nephrotoxic than cisplatin. Based on these data we initiated a phase I clinical trial in patients with refractory metastatic cancer. This report characterizes the pharmacokinetic profile of both the total plasma concentrations of elemental platinum and the unbound ultrafiltrate concentrations of elemental platinum, following a 30 min intravenous infusion of ormaplatin. Platinum concentrations were determined by AAS, and pharmacokinetic parameters for both the total plasma concentration and the ultrafiltrate concentration of elemental platinum were determined using both compartmental and noncompartmental methods. Twenty-eight patients (14 males and 14 females; median age, 58) received ormaplatin. There was a linear relationship between Cmax and dose (r2 = 0.945) and AUC and dose (r2 = 0.976). Ormaplatin is more accurately described by a two-compartment model than by a one-compartment model. The distribution half-life (t1/2 alpha) was 0.3 h and the terminal half-life (t1/2 beta) was 39.1 h. The volume of the central compartment (V) was 68.6 L and the volume of distribution at steady state (Vdss) was 183 L. Like total plasma platinum, unbound platinum is also best characterized by a two-compartment model. The elimination of free platinum is also biphasic with a distribution half-life (t1/2 alpha) of 0.3 h and a terminal half-life (t1/2 beta) of 19.3 h. The mean volume of the central compartment (V) was 200.5 L, and the mean volume of distribution at steady state (Vdss) was 560.5 L. Clinical development of ormaplatin has been terminated due to increased frequency of neurological complications noted over other platinum agents; however, the pharmacokinetics are, in general, similar to those of other clinically used platinum compounds.

Phase II trial of suramin, leuprolide, and flutamide in previously untreated metastatic prostate cancer

PURPOSE

To assess the efficacy and toxicity of suramin, hydrocortisone, leuprolide, and flutamide in previously untreated metastatic prostate cancer.

PATIENTS AND METHODS

Patients with stage D2 and poor-prognosis stage D1 prostate cancer were given suramin on a pharmacokinetically derived dosing schedule to maintain suramin concentrations between 175 and 300 micrograms/mL. Additionally, all patients received flutamide 250 mg orally three times daily, initiated on day 1 and continued until disease progression; depot leuprolide 7.5 mg intramuscularly begun on day 5 and repeated every 4 weeks indefinitely; and replacement doses of hydrocortisone.

RESULTS

Fifty patients were entered onto the study: 48 with stage D2 and two with stage D1 disease. The median age was 59 years (range, 42 to 79) and 31 patients had a Karnofsky performance status (KPS) of 100%. Forty-five patients had bone metastases and 25 had measurable soft tissue disease. Forty-one (82%) had severe disease. The overall response rate in 49 assessable patients was three complete responses (CRs) and 30 partial responses (PRs) for an overall response rate of 67%. Eighteen patients have died. The median survival time has not been reached, with a median potential follow-up duration of 44 months. Grade 3 to 4 toxicity was seen in 38% of patients and was predominantly hematologic and reversible.

CONCLUSION

The high response rate and prolonged survival in a poor-prognosis group of patients with metastatic prostate cancer warrant a phase III randomized comparison of this regimen versus hormonal therapy alone. Toxicity was moderate and reversible.

In vitro effect of gallium nitrate when combined with ketoconazole in the prostate cancer cell line PC-3

Secondary hormonal manipulations are common following the failure of combined androgen blockade in patients with metastatic prostate cancer. Ketoconazole has been shown to have activity in this disease by inhibiting cytochrome P450 steroid hormone biosynthesis, thus inducing androgen deprivation. Gallium nitrate has been reported to target tumor tissue in vitro and some preliminary data suggests activity in patients with prostate cancer. Thus, we conducted a Phase II study of gallium nitrate in patients with androgen-independent prostate cancer. Two patients with progressive prostate cancer were removed from this study and subsequently placed on ketoconazole, as a palliative agent. Surprisingly, both of these patients had a greater than 50% decline in their prostate specific antigen (PSA) with this secondary endocrine maneuver. Based on this clinical observation, we conducted the following in vitro study to determine if there was a substantial additive effect of gallium nitrate followed by ketoconazole. Gallium nitrate or ketoconazole was added to the androgen-independent prostatic epithelial cell line, PC-3. One hundred and twenty hours (120 h) following the addition of one of the agents, the media was aspirated and the second agent was added to the wells. One plate was assayed every 24 h for cell viability using a non-isotopic cell proliferation assay kit. Cells treated with gallium nitrate followed by ketoconazole were 70-100% of control at the end of the gallium nitrate treatment; ketoconazole was then added and viability either remained constant or dropped steadily. Gallium nitrate by itself had a weak inhibitory effect on cell viability that only became apparent at the highest concentration evaluated. Ketoconazole, on the other hand, showed a substantial growth inhibition that was concentration-dependent. Cells treated with this agent alone showed a pronounced steady decrease in viability. Exposure to ketoconazole for 120 h followed by incubation in culture medium alone for 120 h caused a decrease in cell viability to 26.0% of control. Our in vitro results suggest that the combination of gallium nitrate and ketoconazole has no additive activity in the PC-3 cell line. Furthermore, this study confirms that ketoconazole added to prostate cancer cells has antiproliferative activity. The in vitro activity of ketoconazole has traditionally been thought to result from its inhibition of cytochrome P450-dependent enzymes responsible for steroidogenesis; however, an alternative hypothesis is necessary to explain the cytotoxic effect in the absence of adrenal and testicular androgen production as found in an in vitro system.

Initial pharmacokinetics and bioavailability of PSC 833, a P-glycoprotein antagonist

Resistant cancer cells have been shown to overexpress a 170-kd membrane glycoprotein called P-glycoprotein. P-glycoprotein, a product of the multidrug resistance 1 gene, functions as an energy-dependent efflux pump that decreases intracellular drug concentrations. A variety of nonchemotherapeutic agents have been shown to inhibit P-glycoprotein-dependent drug efflux including cyclosporin. PSC 833 is a nonimmunosuppressive derivative of cyclosporin D with the ability to reverse multidrug resistance because of P-glycoprotein overexpression in vitro. As part of early clinical development of PSC 833, the authors investigated the bioavailability of an oral formulation of PSC 833. PSC 833 (3 mg/kg) was administered as a 2-hour intravenous infusion on day 1 of the treatment cycle. Serial blood samples for the determination of PSC 833 whole blood concentrations were obtained after both the intravenous and oral doses. On day 5 of the study, patients received a single oral dose (9 mg/kg) of PSC 833. A total of 14 patients were treated. The intravenous data were best described by a two-compartment open model. The oral data also were described using a two-compartment model, with oral absorption incorporating a lag time to account for possible delays in absorption. There was large intra- and interpatient variability in the pharmacokinetics of PSC 833 in these patients. The absolute bioavailability of PSC 833 was 34% but ranged from 3% to 58% of the administered dose. The clearance (CI) of PSC 833, in general, was consistent between the two dose forms administered. The pharmacokinetic behavior of PSC 833 appears to be similar to that of cyclosporine.

Apoptosis: its role in the development of malignancies and its potential as a novel therapeutic target

OBJECTIVE

To review the current literature regarding the role of apoptosis in the development of malignant cells and how the induction of this pathway could be used in cancer therapy.

DATA SOURCE

A MEDLINE search of basic science articles pertinent to the understanding of the normal physiologic process of apoptosis was conducted.

STUDY SELECTION

Because of the rapidly growing literature regarding apoptosis, only articles describing key processes in the biology of the cell and the genetic control of apoptosis were included.

DATA SYNTHESIS

Apoptosis is imperative for host survival since it discards unwanted, damaged, and atypical cells. The process is therefore implicated in the continuous regulation of development, differentiation, and homeostasis. Furthermore, apoptosis is a response to physiologic and pathologic stresses that disrupt the balanced rates of cell generation and elimination. In a disease such as cancer, there is a lack of equilibrium between the rates of cell division and cell death; agents that promote or suppress apoptosis can manipulate these rates, influencing the anomalous accumulation of neoplastic cells. Pharmacologic manipulation of apoptosis can manipulate these rates, influencing the anomalous accumulation represents a novel approach in targeting malignant cells and has far-reaching implications for new directions in cancer therapy.

CONCLUSIONS

Apoptosis is a highly organized physiologic mechanism of destroying injured and abnormal cells as well as maintaining homeostasis in multicellular organisms. Both the activation and inhibition of apoptosis are tightly controlled. Pharmacologic manipulation of this pathway is a novel therapeutic target in cancer therapy.

New anti-angiogenesis agents: review of the clinical experience with carboxyamido-triazole (CAI), thalidomide, TNP-470 and interleukin-12

Angiogenesis was postulated to be a critical prognostic factor and therapeutic focus for malignancy more than two decades ago. Recent studies indicate quantitative assessments of microvessel count to be an independent prognostic variable for disease-free and overall survival in a wide variety of tumors, and that angiogenesis may be a feasible target against which to intervene pharmacologically. Several new and old agents have been found to have anti-angiogenic activity and have reached clinical trial. This review will focus on four agents under investigation in the US: carboxyamido-triazole (CAI), thalidomide, TNP-470 and interleukin (IL)-12. CAI, originally identified for its anti-invasive capacity, has been shown to inhibit tumor and endothelial cell proliferation by inhibition of calcium uptake. It is administered orally, is generally well tolerated, and has been shown to induce disease stabilization and occasional reductions in tumor mass. Thalidomide was shown to inhibit growth factor-induced neovessel formation, a process that can also explain its earlier devastating clinical toxicity. It is administered orally, and is currently in phase II clinical trials for prostate cancer, glioblastoma multiforme and breast cancer. TNP-470 is a fumagillin analog that has been shown in in vivo models to be a potent inhibitor of angiogenesis at concentrations that are cytostatic to endothelial cells and tumor cells. Lastly, IL-12 may exert its anti-angiogenic effects through activation of interferon-gamma to up-regulate interferon-inducible protein-10, an anti-angiogenic cytokine. Phase I clinical trials of IL-12 have shown disease stabilization in several tumor types in response to s.c. administration or using genetically engineered IL-12-expressing patient fibroblasts. These promising new agents join the matrix metalloproteinase inhibitors as important new drugs in the anti-cancer armamentarium.

The pharmacokinetics of TNP-470, a new angiogenesis inhibitor

STUDY OBJECTIVE

To characterize the pharmacokinetic profile of TNP-470, a synthetic analog of fumagillin that is a potent inhibitor of angiogenesis and inhibits neovascularization in several solid tumor models.

DESIGN

A dose-escalation phase I clinical trial.

SETTING

The National Institutes of Health.

PATIENTS

Patients with human immunodeficiency virus-associated Kaposi's sarcoma.

INTERVENTIONS

The TNP-470 dosage was increased in 13 sequential cohorts using a modified Fibonacci escalation scheme (4.6, 9.3, 15.4, 23.2, and 43.1 mg/m2). The drug was administered as a 1-hour intravenous infusion. Serial blood samples were collected and assayed by reverse-phase high-performance liquid chromatography and the pharmacokinetics were characterized.

MEASUREMENTS AND MAIN RESULTS

There was a linear relationship between the dose of TNP-470 and both area under the curve to infinity (AUC[inf]) and time to maximum concentration (Cmax). The Cmax ranged between 6.6 ng/ml at the lowest dosage (4.6 mg/m2) and 597.1 ng/ml at the highest dosage (43.1 mg/m2). The agent was rapidly cleared from the circulation with a short terminal half-life (0.88 +/- 2.5 hr), which is consistent with preclinical data. Peak plasma concentrations of AGM-1883, an active metabolite, ranged between 0.4 and 158.1 ng/ml.

CONCLUSION

Concentrations of TNP-470 that have in vitro activity were achievable in vivo. The drug was rapidly cleared from the circulation after a single 1-hour infusion. There was considerable interpatient variability in the clearance, but no evidence of saturable elimination. If more prolonged exposure is necessary for activity, administration of TNP-470 by continuous infusion may be suitable.

Plasma protein binding of phenylacetate and phenylbutyrate, two novel antineoplastic agents

Phenylacetate and phenylbutyrate, two novel inducers of tumor cytostasis and differentiation, are currently in clinical trials for the treatment of cancer in adults. The purpose of our study was to evaluate the plasma protein-binding characteristics of phenylacetate and phenylbutyrate in the plasma of normal volunteers and that of patients with cancer. Drug plasma protein-binding analysis was examined using three separate devices: a micropartition system and two equilibrium dialysis systems, all of which exhibited similar results. Phenylacetate and phenylbutyrate concentrations were determined by high-performance liquid chromatography. Both drugs exhibited concentration-dependent binding. Our results showed sodium phenylacetate to have a higher free fraction than sodium phenylbutyrate at corresponding concentrations (> 0.442 +/- 0.008 and > 0.188 +/- 0.001, respectively). Plasma pH did not greatly affect protein binding of either drug. As albumin concentration decreased, an increase in free fraction of both drugs was observed, however alpha 1-acid glyco-protein showed no change in free fraction as its concentration increased. Patients with cancer with lower levels of albumin showed an increase in free fraction with both phenylacetate and phenylbutyrate. When phenylacetate and phenylbutyrate were added together in plasma, the free fraction of phenylacetate increased, whereas the phenylbutyrate free fraction slightly decreased. We conclude that phenylacetate and phenylbutyrate have high free fractions that change with varying albumin levels and when both phenylacetate and phenylbutyrate are present together in plasma.

A phase I/II study of continuous infusion suramin in patients with hormone-refractory prostate cancer: toxicity and response

INTRODUCTION

Suramin is a synthetic polysulfonated naphthylurea which has been used for the treatment of African trypanosomiasis and onchocerciasis, but since the mid-1980s has received attention as a possible antiretroviral and antineoplastic agent.

OBJECTIVE

This clinical trial of suramin was undertaken as a phase I/II study in patients with hormone-refractory prostate cancer, with the hypothesis that the intensity of therapy with suramin could be increased significantly if measures were undertaken to maintain the plasma concentrations of the drug under 300 microg/ml.

METHODS

We report the clinical results of this trial, wherein patients were treated at three different targeted plasma suramin concentrations (275, 215 and 175 microg/ml) for varying periods of time (2, 4 or 8 weeks), with delivery of the drug by continuous intravenous infusion.

RESULTS

The major toxicity observed in this trial was neurologic, consisting of a motor and sensory peripheral neuropathy that resulted in both paresis and paralysis of the limbs. Nearly all of this severe (CTEP grade III, IV) neurologic toxicity was observed in the patients treated at a plasma suramin concentration of 275 microg/ml for 4 or more weeks. A single patient treated at 215 microg/ml for 8 weeks developed moderate (CTEP grade III) proximal lower extremity weakness, and no patient treated at 175 microg/ml developed this toxicity. The second most common toxicity observed was infection of the central venous catheter. The overall response rate for all of the evaluable patients was 17% (13 of 75 patients). In addition, prostate-specific antigen (PSA)-defined responses were observed in six patients receiving therapy at 175 microg/ml, but these responses were confounded by cessation of therapy with flutamide during suramin treatment.

CONCLUSIONS

In summary, although plasma suramin concentrations were maintained below 300 microg/ml, neurologic toxicity nonetheless occurred with high frequency in patients treated at 275 microg/ml for 4 or more weeks. Therapy at 215 and 175 microg/ml was in general well tolerated, but central venous catheter-related infection, as well as the inconvenience and expense of continuous infusional therapy, make this method of drug delivery impractical. Only moderate antitumor activity was observed during this trial, but it is possible that both continuation of flutamide and flutamide withdrawal during suramin therapy confounded the assessment of suramin's activity in hormone-refractory prostate cancer.

A phase I study of pentosan polysulfate sodium in patients with advanced malignancies

BACKGROUND

Pentosan polysulfate (xylanopolyhydrogensulfate) is a semi-synthetic sulfated heparinoid polysaccharide which has been used as an anticoagulant for nearly thirty years in Europe. It antagonizes the binding of bFGF to cell surface receptors and has thus been evaluated for antitumor activity in several animal models and human tumor cell lines. In two angiogenic models pentosan has been shown to inhibit bFGF stimulation of angiogenesis. Previous clinical studies have determined the coagulation effects of pentosan to be the dose-limiting toxicity.

PATIENTS AND METHODS

We conducted a phase I study designed to define the duration-limiting toxicity associated with progressive prolongation of a continuous intravenous infusion (three, five, and eight weeks). This study was not designed to escalate the dose of pentosan beyond that required to maintain the activated partial thromboplastin time (aPTT) between 1.8 and 2.2 times the baseline value.

RESULTS

Thirteen patients with advanced stage metastatic cancer were enrolled (median age 50 years, range 34 to 61 years). Four patients were treated in cohort #1 (three weeks of infusional therapy), five patients were treated in cohort #2 (five weeks of therapy), and four patients in cohort #3 (eight weeks of therapy). All patients experienced a progressive prolongation of their aPTT and PT. Furthermore, all patients experienced at least grade I thrombocytopenia. Other complications were, in general, mild. One patient developed grade III liver abnormalities while receiving the eight-week infusion and another patient developed grade IV thrombocytopenia while receiving the same regimen. One patient with colon cancer had stable disease for 24 weeks, while the remaining 12 patients had no objective evidence of response.

CONCLUSION

Pentosan was well tolerated when doses were adjusted for aPTT prolongations and a five-week cycle appeared to be the maximum tolerated duration of infusion (initially 4 mg/kg/day). One patient had stable disease, but there was no objective tumor response noted in the remaining 12 patients.

The differentiating agent phenylacetate increases prostate-specific antigen production by prostate cancer cells

The prostatic-specific antigen (PSA) is the tumor marker most widely relied upon for the monitoring of patients with prostate cancer. Recently, declines in the serum concentrations of PSA have been advocated as a surrogate marker of tumor response in clinical trials of investigational antitumor agents. We examined the hypothesis that this postulate may not apply to the evaluation of drugs such as phenylacetate, a differentiating agent endowed with mechanisms of action different from those of classic cytotoxic chemotherapy. Using human prostatic carcinoma LNCaP cells as a model, we show that phenylacetate induces PSA production despite inhibition of tumor cell proliferation. Incubation of LNCaP cultures with cytostatic doses of phenylacetate (3-10 mM) resulted in a three- to fourfold increase in PSA secretion per cell. This appears to result from upregulation of PSA gene expression, as indicated by elevated PSA mRNA steady-state levels in treated cells. The increase in PSA production per cell was confirmed in rats bearing subcutaneous LNCaP tumor implants that were treated systemically with phenylacetate. Further comparative studies indicate that upregulation of PSA is common to various differentiation inducers, including all-trans-retinoic acid, 1,25-dihydroxyvitamin D3, and butyrate but is not induced by other antitumor agents of clinical interest such as suramin. We conclude that declines in PSA may be treatment specific and that the exclusive use of this criterion as a marker of disease response may mislead the proper evaluation of differentiating agents in prostate cancer patients.

A phase I study of bolus versus continuous infusion of the anti-CD19 immunotoxin, IgG-HD37-dgA, in patients with B-cell lymphoma

IgG-HD37-SMPT-dgA is a deglycosylated ricin A chain (dgA)-containing immunotoxin (IT) prepared by conjugating the monoclonal murine (MoAb) anti-CD19 antibody, HD37, to dgA using the heterobifunctional hindered disulfide linker, N-succinimidyl-oxycarbonyl-alpha-methyl-alpha-(2-pyridyldithio) toluene (SMPT). In this report, we have used two regimens for the administration of IgG-HD37-SMPT-dgA to patients with non-Hodgkin's lymphoma (NHL) in two concomitant phase I trials. One trial examined four intermittent bolus infusions administered at 48-hour intervals. The other studied a continuous infusion (CI) administered over the same 8-day period. In the intermittent bolus regimen, the maximum tolerated dose (MTD) was 16 mg/m2/8 d and the dose-limiting toxicity (DLT) consisted of vascular leak syndrome (VLS), aphasia, and evidence of rhabdomyolysis encountered at 24 mg/m2/8 d. Using the CI regimen, the MTD was defined by VLS at 19.2 mg/m2/8 d. At the MTD of both regimens, a novel toxicity, consisting of acrocyanosis with reversible superficial distal digital skin necrosis in the absence of overt evidence of systemic vasculitis, occurred in 3 patients. Of 23 evaluable patients on the bolus schedule, there was 1 persisting complete response (CR; > 40 months) and 1 partial response (PR). Of 9 evaluable patients on the continuous infusion regimen, there was 1 PR. Pharmacokinetic parameters for the bolus regimen at the MTD showed a mean maximum serum concentration (Cmax) of 1,209 +/- 430 ng/mL, with a median T1/2 beta for all courses of 18.2 hours (range, 10.0 to 80.0 hours), a volume of distribution (Vd) of 10.9 L (range, 3.1 to 34.5 L), and a clearance (CL) of 0.45 L/h (range, 0.13 to 2.3 L/h). For the CI regimen at MTD, the mean Cmax was 963 +/- 473 ng/mL, with a median T1/2 beta for all courses of 22.8 hours (range, 24.1 to 30.6 hours), a Vd of 9.4 L (range, 4.4 to 19.5 L), and a CL of 0.32 L/h (range, 0.12 to 0.55 L/h). Twenty-five percent of the patients on the bolus infusion regimen and 30% on the CI regimen made antibody against mouse Ig (HAMA) and/or ricin A chain antibody (HARA). We conclude that this IT can be administered safely and that both regimens achieve comparable peak serum concentrations at the MTD; these concentrations are similar to those achieved previously using other regimens with IgG-dgA ITs at their respective MTDs. Thus, toxicity is related to the serum level of the IT and does not differ with different targeting MoAbs.

Suramin-induced neutropenia

This paper presents a retrospective review of 6 cases of severe neutropenia attributed to suramin, the response to granulocyte-colony stimulating factor (G-CSF) and the possible mechanism. Plasma suramin concentrations, G-CSF, platelet-derived growth factor-AB (PDGF-AB) and fibroblast growth factor basic (FGF basic) levels were measured and correlated with neutropenic course. The time course of neutropenia was unpredictable and occurred both during and following discontinuation of suramin. Neutropenia rapidly resolved with G-CSF. Neither the measured growth factor levels nor plasma suramin concentrations correlated with neutropenia. We conclude that neutropenia secondary to suramin is unpredictable and responds to G-CSF administration permitting further suramin therapy. The mechanism remains unknown.

The mutated androgen receptor and its implications for the treatment of metastatic carcinoma of the prostate

Androgen deprivation is the most effective therapy for patients with advanced prostatic carcinoma. The lack of androgen stimulation on these cells causes them to become apoptotic. Although therapeutic efficacy of initial androgen deprivation in prostate cancer is high, the emergence of androgen-independent cancer is inevitable. Withdrawal of the antiandrogen flutamide elicits surprising activity in these cancers. In numerous studies the response rates cell line harbors a mutation in codon 877 of the androgen receptor. The mutant receptor loses androgen specificity and is activated by various steroids as well as flutamide. Identical and similar mutations have now been isolated from human prostate cancer tissue. The discovery of the mutated androgen receptor sheds light on the emergence of androgen-independent cancer and should facilitate the development of more efficacious therapies.

Intravesical suramin: a novel agent for the treatment of superficial transitional-cell carcinoma of the bladder

Patients with recurrent or high-grade superficial transitional-cell carcinoma of the bladder that has recurred after intravesical chemotherapy are at increased risk for tumor invasion and metastases. Intravesical chemotherapy is a minimally invasive technique that allows high doses of therapeutic agents to be delivered directly to the malignancy, doses that would not be tolerated systemically. In vitro studies demonstrate suramin's significant efficacy against transitional-cell carcinoma cell lines at relatively low doses. Humans treated with similar doses delivered in a systemic fashion have experienced no bladder toxicity. Suramin has been shown to block the binding of epidermal growth factor (EGF) to its receptors, which are found in large amounts in bladder cancers. Because a significant association has been found between the number of EGF receptors on a bladder-cancer cell and its sensitivity to suramin, transitional-cell carcinoma could potentially be very responsive to such therapy. On the basis of these findings, a phase I escalating-suramin-dose study is currently being conducted.

Pharmacokinetics of ondansetron in patients with hepatic insufficiency

Ondansetron is primarily eliminated via hepatic metabolism; thus, liver disease may affect its clearance. The pharmacokinetics of ondansetron in patients with different degrees of hepatic insufficiency (N = 12 with hepatic impairment, as categorized by Pugh's classification method) were assessed and the results compared with results for age- and gender-matched control subjects with normal liver function (n = 12). A secondary objective was to correlate the Pugh method of assessing hepatic impairment and quantitative metabolic markers used to assess hepatic function (antipyrine clearance and indocyanine green clearance) with changes in the pharmacokinetics of ondansetron. This was an open-label study in which 8 mg ondansetron was given orally and intravenously, following a randomized crossover design. Clearance of ondansetron was lower among patients with hepatic impairment that control subjects. After a single, oral dose of ondansetron, mean absolute bioavailability increased markedly with increased hepatic insufficiency (approaching 100% in the group with severe hepatic impairment versus 66% for control subjects). These data suggest that there is a reduced first-pass effect in patients with liver disease resulting in a higher AUC0-infinity. A correlation existed between clearance of ondansetron and decreased antipyrine clearance; a smaller correlation existed between ondansetron clearance and indocyanine green clearance. Mean percent of ondansetron bound to plasma proteins was significantly lower in patients with liver disease than in control subjects. None of the patients experienced any severe adverse reactions attributed to ondansetron. A reduction in the clearance of ondansetron is associated with increasing degrees of hepatic insufficiency; therefore, patients with severe hepatic impairment (Pugh score of > 9) should have their daily dose of ondansetron limited to 8 mg (or 0.15 mg/kg).

Phase I study of lovastatin, an inhibitor of the mevalonate pathway, in patients with cancer

Lovastatin, an inhibitor of the enzyme 3-hydroxy-3-methylglutaryl-coenzyme A reductase (the major regulatory enzyme of the mevalonate pathway of cholesterol synthesis), displays antitumor activity in experimental models. We therefore conducted a Phase I trial to characterize the tolerability of lovastatin administered at progressively higher doses to cancer patients. From January 1992 to July 1994, 88 patients with solid tumors (median age, 57 +/- 14 years) were treated p.o. with 7-day courses of lovastatin given monthly at doses ranging from 2 to 45 mg/kg/day. The inhibitory effects of lovastatin were monitored through serum concentrations of cholesterol and ubiquinone, two end products of the mevalonate pathway. Concentrations of lovastatin and its active metabolites were also determined, by bioassay, in the serum of selected patients. Cyclical treatment with lovastatin markedly inhibited the mevalonate pathway, evidenced by reductions in both cholesterol and ubiquinone concentrations, by up to 43 and 49% of pretreatment values, respectively. The effect was transient, however, and its magnitude appeared to be dose independent. Drug concentrations reached up to 3.9 micrometer and were in the range associated with antiproliferative activity in vitro. Myopathy was the dose-limiting toxicity. Other toxicities included nausea, diarrhea, and fatigue. Treatment with ubiquinone was associated with reversal of lovastatin-induced myopathy, and its prophylactic administration prevented the development of this toxicity in a cohort of 56 patients. One minor response was documented in a patient with recurrent high-grade glioma. Lovastatin given p.o. at a dose of 25 mg/kg daily for 7 consecutive days is well tolerated. The occurrence of myopathy, the dose-limiting toxicity, can be prevented by ubiquinone supplementation. To improve on the transient inhibitory activity of this dosing regimen on the mevalonate pathway, alternative schedules based on uninterrupted administration of lovastatin should also be studied.

Severe thrombocytopenia in patients treated with suramin: evidence for an immune mechanism in one

Although suramin has long been used to treat human trypanosomiasis, recent clinical trials have tested its efficacy against the acquired immunodeficiency syndrome (AIDS) and various malignancies. Thromobocytopenia was observed in early trials with suramin in AIDS, but has been uncommon in patients treated for solid tumors. Here we describe 5 patients out of a total of 67 (7%) who developed severe thrombocytopenia while receiving suramin as part of a phase II clinical trial for metastatic prostate carcinoma refractory to hormonal therapy. IgG purified from one patient's plasma caused suramin-dependent platelet aggregation. There was also evidence of crossreactivity between suramin and heparin in this system. An immune mechanism, however, could not be documented in the other cases, suggesting that multiple mechanisms may be responsible for severe thrombocytopenia in this patient population.

Clinical investigation of a cytostatic calcium influx inhibitor in patients with refractory cancers

Carboxyamido-triazole (CAI) is a synthetic inhibitor of non-excitable calcium channels that reversibly inhibits angiogenesis, tumor cell proliferation, and metastatic potential. Inhibition of calcium influx and calcium-dependent events is a potential common mechanism underlying these effects of CAI. The cytostatic and antiangiogenic properties of CAI led to its development for clinical investigation. In a Phase I clinical trial open to patients with refractory solid tumors, 49 patients received p.o. administered CAI daily or every other day. Two oral formulations, PEG-400 CAI solution and a gelatin capsule containing CAI in PEG-400, were tested. All administered dosages of CAI yielded plasma concentration at or above the range demonstrated to be effective in inhibiting signaling and cancer progression in vitro and in preclinical models (1 microgram/ml, 2.3 microM). Toxicity of p.o. administered CAI most commonly consisted of dose-related grade 1-2 nausea, vomiting, and occasional anorexia. CAI administration at bedtime ameliorated gastrointestinal complaints in many patients; others required addition of simple antiemetic regimens, usually consisting of metoclopropamide or prochlorperazine. Gastrointestinal complaints were the cause for compliance-limiting toxicity at 175 mg/m2/day of the liquid formulation and 125 mg/m2/day of the gelatin capsule formation. Reversible and rare sensory axonal neuropathy (grade 3, 1 patient) and neutropenia (grade 4, 1 patient) were dose-limiting toxicities observed at the 330 mg/m2 every-other-day liquid CAI dose level. No evidence of cumulative end organ damage or central nervous system injury was observed. Disease stabilization and improvement in performance status was observed. Disease stabilization and improvement in performance status was observed in 49% of evaluable patients who had disease progression before CAI. Disease stabilization and associated improvement in performance status was seen in patients with renal cell carcinoma (7 months), pancreaticobiliary carcinomas (3, 5, and 5 months), melanoma (7 months), ovarian cancer (7 months), and non-small cell lung cancer (3 months). The recommended Phase II doses from this trial are 150 mg/m2/day in the liquid formation and 100 mg/m2/day in the gelatin capsule formation.

Lack of correlation between prostate-specific antigen and the presence of measurable soft tissue metastases in hormone-refractory prostate cancer

Appropriate staging procedures for patients with hormone-refractory prostate cancer are poorly defined. In particular, there are no studies correlating prostate-specific antigen (PSA) with more traditional methods of staging. We have evaluated the abdominal/pelvic CT scan, bone scan, and PSA results following initial diagnosis of hormone-refractory prostate cancer in 177 consecutive patients (median age = 63.1 years, range 45-80). Thirty-four patients (19.2%) had measurable lesions (> or = 2 cm) on CT scan compatible with metastatic disease. Of the patients with measurable lesions, 29/34 (85.3%) had retroperitoneal and/or pelvic adenopathy; 5 patients (14.7%) had measurable lesions in the liver. Other sites of metastatic disease were detected in less than 1% of the patients receiving scans. All patients had bone scan abnormalities compatible with metastatic disease. Results of these imaging studies were then compared to PSA serum concentration (Abbott IMx). The mean PSA concentration was not different in those patients with soft tissue disease as compared to those without soft tissue involvement and there was no correlation between PSA concentration and the presence or absence of measurable soft tissue disease. In contrast to previously published studies in hormone-naïve prostate cancer patients, these studies in hormone-refractory patients indicate that the detection of metastatic disease by standard radiological procedures cannot be predicted by measurement of serum PSA.

Effects of the antiestrogen tamoxifen on low-density lipoprotein concentrations and oxidation in postmenopausal women

Our study demonstrates that tamoxifen, when administered to postmenopausal women at a conventional dosage, reduces LDL levels and protects LDL from oxidation. The protective effect of tamoxifen against the development of breast cancer in women considered at risk is being investigated in a placebo-controlled trial sponsored by the National Institutes of Health. Whether tamoxifen also protects against the development of cardiovascular disease in this trial is also of considerable interest.

Comparison of quantitative methods to assess hepatic function: Pugh's classification, indocyanine green, antipyrine, and dextromethorphan

STUDY OBJECTIVES

To compare three quantitative metabolic markers used to assess hepatic function, indocyanine green (ICG), a high-extraction marker; antipyrine, a low-extraction marker; and dextromethorphan, a P-450IID6 marker, with the clinically used Pugh's classification.

DESIGN

Comparison of 12 healthy controls with 12 age- and sex-matched patients with different degrees of liver disease.

SETTING

Research center in a university-affiliated teaching hospital.

PATIENTS

The 12 patients had different degrees of liver disease: 4 mild (Pugh's score 6 or 7); 4 moderate (Pugh's score 8 or 9); and 4 severe (Pugh's score > or = 10). Each level had an equal number of men and women subjects.

MEASUREMENTS AND MAIN RESULTS

Clearance of ICG detected mild alterations in hepatic function as efficiently as it did for moderate and severe impairment, but it lacked the specificity to distinguish among the classification groups. In contrast, antipyrine was effective in identifying moderate and severe hepatic impairment; however, its clearance was not reduced in mild liver disease. Pugh's classification appears to be a clinically useful method of assessing the global degree of hepatic impairment in patients with chronic disease, and there was a significant correlation between it and antipyrine clearance (r = 0.67, p = 0.0003) and ICG clearance (r = 0.86, p = 0.0001). Four of eight patients with a Pugh's score greater than 8 had a dextromethorphan metabolic ratio expression reflective of a poor metabolizer phenotype based on 0- to 4-hour urine collection, but only two of those eight patients were classified as poor metabolizers based on 4- to 12-hour urine collection. These percentages of poor metabolizers are substantially higher than for historical controls (8.5-10.4%) and most likely reflect a decrease in the P-450IID6 functional ability with progression of liver disease. However, due to small sample size and lack of knowledge of the patients' genotypes, these data are only suggestive.

CONCLUSION

Pugh's classification appears to be a reliable indicator of the degree of chronic liver disease and could be employed as a drug development research classification tool; however, it does not replace quantitative metabolic markers, especially isozyme-specific markers.

Pharmacologic variables associated with the development of neurologic toxicity in patients treated with suramin

PURPOSE

To describe pharmacologic variables correlated with the development of neurologic toxicity in patients treated with suramin.

METHODS

Eighty-one patients were treated with suramin in a phase I study. The rate of drug infusion was continuously adjusted to maintain a preassigned plasma suramin concentration (175, 215, or 275 micrograms/mL) for a fixed duration (2 to 8 weeks).

RESULTS

Eight patients developed grade III/IV neurologic motor impairment (predominantly motor axonal polyneuropathy). All were treated at the 275-micrograms/mL concentration. One patient treated at the 215-micrograms/mL concentration developed grade II motor dysfunction. In addition, seven of nine patients had sensory symptoms. Pharmacologic variables associated with the development of polyneuropathy included total cumulative suramin dose, duration of exposure to plasma concentrations greater than 200 micrograms/mL, and area under the curve (AUC) greater than 200 micrograms/mL.

CONCLUSION

Significant neurologic toxicity can result from therapy with suramin, even when dosing is designed to avoid exposure to plasma concentrations greater than 350 micrograms/mL. Future clinical trials of suramin should be designed in such a way as to limit the total cumulative dose to < or = 157 mg/kg given over a period of > or = 8 weeks, limit the period of exposure to plasma suramin concentrations greater than 200 micrograms/mL to < or = 25 days, and limit the AUC greater than 200 micrograms/mL to < or = 48,000 mg.h/AL.

Pharmacokinetics of orally administered carboxyamido-triazole, an inhibitor of calcium-mediated signal transduction

Carboxyamido-triazole (CAI), inhibits proliferation, invasion, and metastatic potential of a number of cancer cell lines at concentrations greater than 0.4 microgram/ml. The objective of this study was to characterize the pharmacokinetic profile from the first Phase I clinical trial of CAI for the single test dose and multiple daily dosing schedule. Two different p.o. formulations (liquid and gelcap) of CAI were administered. Thirty-nine patients with cancer were enrolled. The dose escalation schema was 100, 125, and 150 mg/m2/day and 200 and 330 mg/m2 every other day of the liquid formulation, plus 100 and 125 mg/m2/day and 200 mg/m2 every other day of the gelcap. The CAI pharmacokinetics are best described by a two-compartment open linear model. The gelcap was more rapidly absorbed than the liquid [time to maximum plasma concentration (Tmax) = 2.06 +/- 1.02 versus 5.31 +/- 3.59 h, P2 = 0.0012] which resulted in higher peak plasma concentrations. There was no evidence of saturable elimination as the dose was increased. The mean steady-state peak concentration was 5.1 +/- 1.0 microgram/ml for the 150 mg/m2/day multiple daily dosing regimen. The terminal half-life of CAI was relatively prolonged, 111 h, and the total body p.o. clearance was low (1.87 liters/h). The peak concentration for all dose levels explored was greater than the targeted concentration suggested by in vitro data for activity. Thus, these data suggest that an effective cytostatic exposure of CAI may be obtained with daily or every other day dosing without severe toxicity.

Antitumor activity of suramin in hormone-refractory prostate cancer controlling for hydrocortisone treatment and flutamide withdrawal as potentially confounding variables

BACKGROUND

A prospective Phase II clinical trial was conducted to assess the clinical activity of a pharmacokinetically guided suramin regimen in patients who had documented progression of metastatic prostate cancer after hydrocortisone plus antecedent or simultaneous withdrawal of flutamide.

METHODS

Fifty-four patients whose disease had progressed after castration and flutamide administration were enrolled on this trial. The study was divided into two parts. Initially, 52 patients received hydrocortisone (30 mg/day) and for those patients receiving flutamide, at study entry (34 patients) flutamide was simultaneously discontinued. Forty-three patients whose disease progressed on hydrocortisone received suramin for 6-8 weeks. Six patients who progressed on hydrocortisone became ineligible for suramin due to clinical deterioration, four patients are still responding to hydrocortisone at more than 1 year, and one patient elected to postpone initiation of suramin. Suramin was given as intermittent infusions at fixed doses on days 1-5 and thereafter dosing was guided by adaptive control with feedback to maintain plasma suramin concentrations between 300-175 micrograms/ml. Antitumor activity was assessed by prostate specific antigen (PSA) decline and soft-tissue disease response.

RESULTS

Ten patients (19%; 95% CI, 9.6%-32.5%) responded to hydrocortisone therapy with either a 50% or greater PSA decline for at least 4 weeks (9 patients) and/or a partial response of measurable soft-tissue disease (2 patients). Five of these patients (10%) demonstrated a 80% or greater PSA decline. All responders to hydrocortisone had simultaneous flutamide withdrawal, and had been receiving flutamide as part of initial combined androgen blockade. Seven of 37 evaluable patients (19%; 95% CI, 8.0%-35.2%) responded to suramin with a 50% or greater decline in PSA for 4 weeks or longer. One patient (3%) had a 80% or greater decline in PSA. There were no soft-tissue disease responses to suramin. The median time to progression was 1.9 months for hydrocortisone therapy and 2.6 months for suramin therapy. The median survival for all patients was 14.6 months.

CONCLUSION

Suramin has antitumor activity in metastatic prostate carcinoma independent of the therapeutic effect of hydrocortisone administration or flutamide withdrawal. The role of prior flutamide withdrawal and hydrocortisone replacement should be taken into account in future studies of suramin.

Phase I study of phenylacetate administered twice daily to patients with cancer

BACKGROUND

The growth-inhibiting and differentiating effects of sodium phenylacetate against hematopoietic and solid tumor cell lines has aroused clinical interest in its use as an anticancer drug. In an earlier Phase I trial of phenylacetate aimed at maintaining serum drug concentrations in the range that proved active in vitro (> 250 micrograms/ml) for 2 consecutive weeks, infusion rates approached the maximum velocity of drug elimination and commonly resulted in drug accumulation and reversible dose-limiting neurologic toxicity. In this study, the authors described the nonlinear pharmacokinetics, metabolism, toxicity, and clinical activity of phenylacetate.

METHODS

The treatment regimen of this Phase I study was designed to expose patients intermittently to drug concentrations exceeding 250 micrograms/ml and to allow time for drug elimination to occur between doses to minimize accumulation. Sodium phenylacetate was administered as a 1-hour infusion twice daily (8 a.m., 5 p.m.) at two dose levels of 125 and 150 mg/kg for a 2-week period. Therapy was repeated at 4-week intervals for patients who did not experience dose-limiting toxicity or disease progression.

RESULTS

Eighteen patients (4 of whom previously were treated with phenylacetate by continuous intravenous infusion) received 27 cycles of therapy. Detailed pharmacokinetic studies for eight patients indicated that phenylacetate induced its own clearance by a factor of 27% in a 2-week period. Dose-limiting toxicity, consisting of reversible central nervous system depression, was observed for three patients at the second dose level. One patient with refractory malignant glioma had a partial response, and one with hormone-independent prostate cancer achieved a 50% decline in prostate specific antigen level, which was maintained for 1 month.

CONCLUSIONS

Phenylacetate administered at a dose of 125 mg/kg twice daily for 2 consecutive weeks is well tolerated. High grade gliomas and advanced prostate cancer are reasonable targets for Phase II clinical trials.

Phase I study of phenylacetate administered twice daily to patients with cancer

BACKGROUND

The growth-inhibiting and differentiating effects of sodium phenylacetate against hematopoietic and solid tumor cell lines has aroused clinical interest in its use as an anticancer drug. In an earlier Phase I trial of phenylacetate aimed at maintaining serum drug concentrations in the range that proved active in vitro (> 250 micrograms/ml) for 2 consecutive weeks, infusion rates approached the maximum velocity of drug elimination and commonly resulted in drug accumulation and reversible dose-limiting neurologic toxicity. In this study, the authors described the nonlinear pharmacokinetics, metabolism, toxicity, and clinical activity of phenylacetate.

METHODS

The treatment regimen of this Phase I study was designed to expose patients intermittently to drug concentrations exceeding 250 micrograms/ml and to allow time for drug elimination to occur between doses to minimize accumulation. Sodium phenylacetate was administered as a 1-hour infusion twice daily (8 a.m., 5 p.m.) at two dose levels of 125 and 150 mg/kg for a 2-week period. Therapy was repeated at 4-week intervals for patients who did not experience dose-limiting toxicity or disease progression.

RESULTS

Eighteen patients (4 of whom previously were treated with phenylacetate by continuous intravenous infusion) received 27 cycles of therapy. Detailed pharmacokinetic studies for eight patients indicated that phenylacetate induced its own clearance by a factor of 27% in a 2-week period. Dose-limiting toxicity, consisting of reversible central nervous system depression, was observed for three patients at the second dose level. One patient with refractory malignant glioma had a partial response, and one with hormone-independent prostate cancer achieved a 50% decline in prostate specific antigen level, which was maintained for 1 month.

CONCLUSIONS

Phenylacetate administered at a dose of 125 mg/kg twice daily for 2 consecutive weeks is well tolerated. High grade gliomas and advanced prostate cancer are reasonable targets for Phase II clinical trials.

Continuous infusion of the anti-CD22 immunotoxin IgG-RFB4-SMPT-dgA in patients with B-cell lymphoma: a phase I study

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

Paclitaxel (taxol) inhibits protein isoprenylation and induces apoptosis in PC-3 human prostate cancer cells

Paclitaxel was examined for its effects on cell survival, internucleosomal DNA fragmentation, and protein isoprenylation in the human prostate cancer cell line PC-3. Treatment of cells with paclitaxel at 5-60 nM for 24 hr resulted in a dose-dependent inhibition of cell viability (IC50, 31.2 nM), which was partially prevented by supplementing the cell culture medium with two nonsterol polyisoprenyl compounds, farnesyl-pyrophosphate (-PP) and geranylgeranyl-PP (3 microM each). Furthermore, agarose gel electrophoresis of DNA extracted from cells treated with paclitaxel (15-60 nM) for 24 hr showed DNA laddering with production of fragments of 180-base pair multiples, indicating the occurrence of apoptotic cell death. Internucleosomal DNA fragmentation by paclitaxel was also detected by a photometric enzyme immunoassay using antihistone antibodies; if culture medium was supplemented with farnesyl-PP and geranylgeranyl-PP (3 microM each), a reduction in mono- and oligonucleosome production was observed. The post-translational incorporation of metabolites of (RS)-[5-3H]mevalonolactone (100 microCi/ml) into prenylated proteins of PC-3 cells was inhibited by paclitaxel at 30 and 60 nM. In addition, the immunoprecipitation of p21ras and p21rap-1 proteins from PC-3 cells exposed to paclitaxel (30 and 60 nM) and labeled with (RS)-[5-3H]mevalonolactone showed a substantial inhibition of the incorporation of farnesyl and geranylgeranyl prenoid groups, respectively, into the aforementioned proteins. These results indicate that the inhibition of protein isoprenylation is a novel component of the complex biochemical effects of the drug and plays an important role in the mechanism of paclitaxel cytotoxicity in PC-3 cells.