Biomedical subjects

L M Reyno

Publications and source records attributed to L M Reyno.

11 recordsLinked to original sources

PubMed1995

Effects of storage on the binding of carboplatin to plasma proteins.

Plasma ultrafiltrates are routinely used in pharmacokinetic studies of carboplatin. Experiments were performed to detect and quantitate artifactual decreases in the platinum concentration of ultrafiltrates prepared from plasma samples stored at -20 degrees C and -70 degrees C. Carboplatin was added to anticoagulated, whole human blood to produce a 20 microgram/ml concentration. Plasma produced from the blood was stored frozen at either -20 degrees C or -70 degrees C. Aliquots from each storage condition were thawed and ultrafiltered once a week for up to 100 days. Platinum concentrations in ultrafiltrates and plasma were determined by flameless atomic absorption spectrometry. There was no loss of ultrafilterable platinum in plasma samples stored at -70 degrees C, whereas there was a steady decrease in free platinum concentration in ultrafiltrates prepared from plasma samples stored at -20 degrees C. These results imply that pharmacokinetic studies of carboplatin should use ultrafiltrates prepared immediately or that plasma for such studies should be stored at -70 degrees C. Storage of carboplatin-containing plasma at -20 degrees C and subsequent ultrafiltration is not acceptable, because measurement of platinum in such ultrafiltrates will be artifactually low.

Blood Preservation↗

PubMed1995

Evaluation of prostate-specific antigen as a surrogate marker for response of hormone-refractory prostate cancer to suramin therapy.

PURPOSE: We evaluated the surrogate role of serum prostate-specific antigen (PSA) using prospectively collected information from patients with hormone-refractory prostate cancer (HRPC) treated with suramin. MATERIALS AND METHODS: Data from 103 patients were analyzed using survival analysis, exploratory analysis, and regression analysis. RESULTS: There was a significant survival difference between groups of patients with a PSA decrease of < or = 0% or greater than 0% (P = .018). There were no significant overall survival differences between groups of patients with PSA decreases less than 50% or > or = 50% and less than 75% or > or = 75%. Tree-based modeling did not define a specific threshold percentage PSA change as a response criterion. For a response of 1-year survival, sensitivity increased (0.91 v 0.69), but specificity decreased (0.37 v 0.62), with a 75% versus 50% PSA decrease used as classification criterion. Differences between the area under the receiver-operating curves (ROCs) with 50% and 75% PSA decreases as threshold values were small. For a response of 1-year survival, attributable proportions were 0.38 and 0.68, respectively, with 50% and 75% PSA decreases as threshold values. When pretreatment variables were assessed by Cox proportional hazards model, hemoglobin level was the most significant predictor of survival. When percentage PSA change was included in the model, hemoglobin level remained the most significant factor, but percentage PSA change was also a weak, but statistically significant, factor. PSA was a weak, but statistically significant, predictor of survival in Cox proportional hazards model with PSA as a time-variant covariate. CONCLUSION: Reduction in PSA level has weak prognostic significance with respect to survival in HRPC patients, but, currently, PSA reduction cannot be used as a reliable response criterion to evaluate treatment efficacy in individual patients. Prospective, randomized studies, including prospective measurement of other indices related to symptomatic clinical benefits, are required.

Adult↗

PubMed1995

Phase I and clinical evaluation of a pharmacologically guided regimen of suramin in patients with hormone-refractory prostate cancer.

PURPOSE: This phase I study was designed with the following objectives: (1) to describe the overall and dose-limiting toxicity (DLT) of suramin administered by intermittent short intravenous infusions until DLT or disease progression; (2) to determine the ability of an adaptive control with feedback (ACF) dosing strategy to maintain suramin plasma concentrations within a preselected range; (3) to develop a population model of suramin pharmacokinetics; and (4) to identify preliminary evidence of antitumor activity. PATIENTS AND METHODS: Seventy-three patients with advanced, incurable, solid tumors (including 69 with hormone-refractory prostate cancer) received an initial 5- to 7-day daily loading treatment followed by intermittent infusions individually determined by ACF using a Bayesian algorithm and relying on population models of suramin pharmacokinetics. Treatment was given to three cohorts of patients based on target plasma suramin concentration ranges (peak, 30 minutes postsuramin, and trough on morning of the treatment day), as follows: cohort 1, 175 to 300 micrograms/mL (27 patients); cohort 2, 150 to 250 micrograms/mL (23 patients); and cohort 3, 100 to 200 micrograms/mL (23 patients). All patients were to receive suramin until DLT or disease progression. RESULTS: The DLT was most commonly seen in cohort 1 and included a syndrome of malaise and fatigue, associated with weight loss, anorexia, and changes in taste. Other reversible toxicities were neurologic, renal, cutaneous, edema, lymphopenia and anemia, ophthalmologic, and alopecia. Forty of 67 assessable patients (60%) had a 50% reduction and 25 of 67 (37%) a 75% reduction in prostate-specific antigen (PSA) levels that lasted more than 4 weeks, seven of 18 (40%) had measurable responses, and 18 of 37 (49%) demonstrated major pain improvement. The overall times to disease progression and survival were 170 and 492 days, respectively. CONCLUSION: We have characterized all toxicities with suramin in a pharmacologically guided phase I study designed to maintain plasma suramin concentrations of 100 to 300 micrograms/mL (cohorts 1 to 3). The incidence of grade 3 to 4 neurologic abnormalities was relatively low, particularly in cohorts 2 and 3 (100 to 250 micrograms/mL). Evidence of significant and durable antitumor activity was seen in all three cohorts.

Adaptation, Physiological↗

PubMed1995

Development and validation of a pharmacokinetically based fixed dosing scheme for suramin.

PURPOSE: We used population pharmacokinetic-parameter estimates and designed a fixed dosing schedule to maintain plasma suramin concentrations between 100 and 300 micrograms/mL and then evaluated its performance. MATERIALS AND METHODS: On day 1, patients received a 200-mg test dose and 1,000-mg/m2 loading dose. On days 2, 3, 4, and 5, patients received 1-hour infusions of 400, 300, 250, and 200 mg/m2, respectively. Subsequent 1-hour infusions of 275 mg/m2 were given on days 8, 11, 15, 19, 22, 29, 36, 43, 50, 57, 67, and 78. Therapy was discontinued for dose-limiting toxicity (DLT) or progressive disease (PD). Patients were to be removed from the fixed dosing schedule if, after day 5, three consecutive peak plasma suramin concentrations were greater than 300 micrograms/mL. RESULTS: Forty-two patients, including 40 with hormone-refractory prostate cancer (HRPC), received 700 infusions. Forty patients were assessable for toxicity; 38 were assessable for response. Two patients with preexisting pulmonary disease died early of respiratory insufficiency. Treatment was discontinued in five patients due to DLT and in seven due to PD. No patient had treatment discontinued due to repeated peak plasma suramin concentrations > or = 300 micrograms/mL. The fixed dosing schedule was precise, unbiased, and well tolerated. DLT consisted of grade 4 nephrotoxicity (n = 2), neurotoxicity (n = 2), and corticosteroid-induced psychosis (n = 1). Three patients, who received all 18 doses of suramin per protocol, developed severe, but not dose-limiting, malaise, fatigue, and lethargy. Twenty-four of 36 assessable patients with elevated serum prostate-specific antigen (PSA) levels had a > or = 50% reduction, lasting more than 4 weeks, and 18 had a > or = 75% reduction, lasting more than 4 weeks. Twelve of 23 (52%) symptomatic HRPC patients noted a subjective improvement in pain. There were no measurable responses in four patients with measurable disease. The estimated median survival time in 38 assessable patients with HRPC was 18.8 months. The estimated median time to progression in 35 patients, for whom data were available, was 10.1 months. CONCLUSION: This easily implemented schedule allowed suramin to be administered safely as an intermittent bolus injection. Toxicity was manageable and reversible.

Adult↗

PubMed1994

Potentiation by interleukin 1 alpha of cisplatin and carboplatin antitumor activity: schedule-dependent and pharmacokinetic effects in the RIF-1 tumor model.

We have previously demonstrated that the cytokine interleukin 1 alpha (IL-1 alpha) significantly potentiates the antitumor activity of a variety of chemotherapeutic agents, including cisplatin (cDDP). In studies described here, we examined the potential of combining IL-1 alpha and the platinum analogue carboplatin (CBDCA) and compared the schedule-dependent and pharmacokinetic effects for IL-1 alpha combinations with cDDP and CBDCA. RIF-1 tumor-bearing mice (C3H/HeJ) received i.p. injections of varying doses of CBDCA, alone or concurrently with IL-1 alpha (48 or 480 micrograms/kg). Clonogenic cell kill and tumor regrowth delay were significantly increased when CBDCA was combined with IL-1 alpha, at both doses, compared to either CBDCA or IL-1 alpha alone (P < 0.001 and P < 0.01, respectively). Although pretreatment with IL-1 receptor antagonist blocked the acute tumor hemorrhagic response induced by IL-1 alpha alone, IL-1 receptor antagonist only partially blocked IL-1 alpha enhancement of CBDCA or cDDP-mediated tumor cell kill. The IL-1 alpha enhancement of CBDCA-mediated tumor cell kill was highly schedule dependent, with maximum antitumor activity observed when IL-1 alpha was administered 4-12 h before CBDCA. In contrast, administration of IL-1 alpha from 24 h before or as late as 6 h after cDDP resulted in the same antitumor activity as simultaneous administration of cDDP and IL-1 alpha. Tumor and normal tissue platinum content were significantly increased by IL-1 alpha in animals treated with CBDCA (P < 0.01) but not in those treated with cDDP. The observed differences between cDDP and CBDCA may be explained by their known differential rates of clearance and protein binding affinities and are compatible with an induced alteration in CBDCA pharmacokinetics.

Animals↗

PubMed1994

Suramin.

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Drug Administration Schedule↗

PubMed1994

Suramin: development of a population pharmacokinetic model and its use with intermittent short infusions to control plasma drug concentration in patients with prostate cancer.

PURPOSE: This study aimed to (1) develop a population pharmacokinetic model for suramin; (2) use Bayesian methods to assess suramin pharmacokinetics in individual patients; (3) use individual patients' pharmacokinetic parameter estimates to individualize suramin dose and schedule and maintain plasma suramin concentrations within predetermined target ranges; and (4) assess the feasibility of outpatient administration of suramin by intermittent, short infusions. METHODS: Plasma suramin concentrations were measured by high-performance liquid chromatography (HPLC), and compartmental pharmacokinetic models were fit using a Bayesian algorithm. Population pharmacokinetic models were developed using an iterative two-stage approach. Estimates of each patient's central-compartment volume were used to calculate suramin dosage. Simulation of that patient's suramin clearance was used to predict the time of his next dose. Using this approach, plasma suramin concentration was maintained at between 200 and 300, 175 and 275, 150 and 250, or 100 and 200 microgram/mL in four sequential patient cohorts. The ability of two- and three-compartment, open, linear models to fit the pharmacokinetic data was compared. Population pharmacokinetic parameters were estimated, using both two- and three-compartment structural models in 69 hormone-refractory prostate cancer patients. RESULTS: Target plasma suramin concentrations in individual patients were rapidly achieved. Concentrations were maintained within desired ranges for > or = 85% of treatment duration in all cohorts. A three-compartment, open, linear model described suramin pharmacokinetics better than did a two-compartment, open, linear model. Population pharmacokinetic estimates generated for two- and three-compartment pharmacokinetic models demonstrated modest interpatient pharmacokinetic variability and the long terminal half-life of suramin. CONCLUSION: Suramin can be administered by intermittent short infusion. Adaptive-control-with-feedback dosing facilitated precise control of plasma suramin concentrations and allowed a number of different concentration ranges to be studied. This approach is expensive and labor-intensive. Although we have demonstrated the ability to control drug exposure, simpler dosing schedules require critical evaluation. Population pharmacokinetic parameters generated in men with hormone-refractory prostate cancer will facilitate rational design of such schedules.

Adult↗

PubMed1994

Modeling toxicity and response in carboplatin-based combination chemotherapy.

Data from women with advanced ovarian cancer (International Federation of Gynecology and Obstetrics stage III or IV) were analyzed to evaluate the pharmacokinetic/pharmacodynamic relationships of carboplatin-based combination chemotherapy. With the equation area under the plasma concentration versus time curve (AUC) = dose/(creatinine clearance + 25), carboplatin AUC was calculated in each of up to six treatment cycles in 224 women with advanced ovarian cancer who had been randomized to receive carboplatin 300 mg/m2 plus cyclophosphamide 600 mg/m2. In addition, for each patient, the predicted nadir count (obtained by rearranging the University of Maryland single-agent carboplatin dosing formula) was compared with the actual observed nadir count, received and relative received dose intensities were calculated, and carboplatin exposure intensity was defined. Relationships were sought between these treatment indices and the clinical outcomes of time to progression and survival. When combined with cyclophosphamide 600 mg/m2, any carboplatin AUC was found to be associated with greater myelotoxicity and a higher likelihood of both leukopenia and thrombocytopenia occurring than had been determined for single-agent carboplatin. Furthermore, the platelet nadir in 83% of patients was equal to or below that predicted to result from the same dose of single-agent carboplatin. There was a relatively narrow range of received dose intensities within this patient population, but carboplatin exposure intensity was calculated as being distributed over a two-fold range within the population. Therefore, received carboplatin dose intensity underestimates the range of plasma drug exposure associated with a fixed dosing regimen of carboplatin. However, there were no consistent relationships between received dose intensity, relative received dose intensity, or carboplatin exposure intensity and the clinical outcomes of time to progression or survival. The relationships between carboplatin exposure and the pharmacodynamic measures of toxicity and response are likely to require definition in each regimen that includes carboplatin and for each tumor type treated.

Antineoplastic Combined Chemotherapy Protocols↗

PubMed1993

Suramin, an active drug for prostate cancer: interim observations in a phase I trial.

BACKGROUND: Previous studies indicate that suramin may be an active agent for treatment of solid tumors. The clinical use of suramin is complicated by a broad spectrum of toxic effects and complex pharmacology. Studies have suggested that the dose-limiting neurotoxicity of this agent is closely related to sustained plasma drug concentrations of 350 micrograms/mL or more. PURPOSE: This phase I clinical trial in patients with solid tumors was designed to determine whether plasma concentrations resulting in both antitumor activity and manageable toxicity could be achieved with short, intermittent infusions of suramin. METHODS: Thirty-seven patients, including 33 with metastatic, hormone-refractory prostate cancer, collectively received 43 courses of suramin designed to maintain a plasma concentration range of 200-300, 175-275, or 150-250 micrograms/mL. Patients received a test dose of 200 mg and an initial loading dose of 1000 mg/m2 on day 1 of therapy. Subsequent suramin doses and schedules were individually determined using a strategy of adaptive control with feedback, which used a maximum a posteriori Bayesian algorithm to estimate individual pharmacokinetic parameters. Patients were treated until dose-limiting toxicity or progressive disease developed. RESULTS: Thirty-five of the 37 study patients and 31 of the 33 with prostate cancer were assessable for toxicity and response. Treatment was discontinued in 28 patients because of dose-limiting toxicity consisting of a syndrome of malaise, fatigue, and lethargy; recurrent reduction in creatinine clearance of 50% or more; or axonal neuropathy. Evidence of major antitumor activity was observed in patients with prostate cancer treated at all three plasma drug concentrations. Measurable responses (one complete response and five partial responses) were noted in six of 12 patients with measurable disease. Twenty-four (77%) of 31 patients had a reduction in prostate-specific antigen of 50% or more, and 17 (55%) of 31 had a reduction of 75% or more. Twenty (83%) of 24 patients reported reduction in pain. CONCLUSIONS: Suramin can be safely administered as an intermittent bolus injection by use of adaptive control with feedback to control plasma drug concentrations; toxicity is significant but manageable and reversible. Suramin is active against hormone-refractory prostate cancer. IMPLICATIONS: Future trials should address the role and necessary extent of therapeutic drug monitoring; the optimal plasma drug concentration range and duration of therapy; and the activity of suramin in combination with other agents, in earlier stages of prostate cancer, and in other tumor types.

Aged↗

PubMed1993

Impact of cyclophosphamide on relationships between carboplatin exposure and response or toxicity when used in the treatment of advanced ovarian cancer.

PURPOSE: To determine (1) the impact of cyclophosphamide 600 mg/m2 on previously defined relationships between carboplatin area under the plasma concentration versus time curve (AUC) and indices of toxicity and response in women with advanced ovarian cancer; and (2) the relationships between indices of cumulative drug exposure and clinical outcomes. METHODS: Carboplatin AUC = dose/(creatinine clearance [CCr] + 25) and was calculated in 224 women who received carboplatin 300 mg/m2 and cyclophosphamide 600 mg/m2. The likelihood of grade 3 or greater myelotoxicity at any carboplatin AUC was compared with the likelihood of myelotoxicity at the same single-agent carboplatin AUC. The nadir count predicted using the University of Maryland single-agent carboplatin dosing formula was compared with the nadir count observed. Received and relative-received dose-intensity were calculated. Carboplatin exposure-intensity was defined by substituting cumulative carboplatin exposure for total dose. Relationships were sought between these indices and therapeutic outcomes. RESULTS: The incidence of leukopenia and thrombocytopenia at any carboplatin AUC was greater for the two-drug combination than for single-agent carboplatin. The platelet nadir in 83% of patients was less than or equal to the nadir predicted for the same single-agent carboplatin AUC. Despite a narrow range of received dose-intensities, carboplatin exposure-intensity was distributed over a twofold range. There were no relationships between received and relative-received dose-intensity or carboplatin exposure-intensity and time to progression or survival. CONCLUSION: Any carboplatin AUC when administered with cyclophosphamide 600 mg/m2 produces greater myelotoxicity than the same AUC of single-agent carboplatin. Received carboplatin dose-intensity underestimates the range of plasma drug exposure resulting from a fixed carboplatin dosing regimen. Whether higher carboplatin exposures can improve outcome requires prospective validation.

Adult↗

PubMed1992

Chemotherapy induced amenorrhoea in a randomised trial of adjuvant chemotherapy duration in breast cancer.

We have previously reported the results of a clinical trial in patients with stage II breast cancer which compared a 12 week chemohormonal regimen with a 36 week chemotherapy regimen. Both pre and post menopausal women were entered. The 12 week regimen was inferior both in terms of disease-free survival and overall survival. The effect of chemotherapy on menstrual function was prospectively documented in 95 of 114 premenopausal women at 3 of the 4 participating centres. 67 of the 95 women (70.5%) developed permanent amenorrhoea. There was a statistically significant difference in the rate of induced amenorrhea between the 12 week and the 36 week groups; 23/42 vs. 44/53, respectively (P = 0.003). Recurrence and mortality rates were lower in the patients who became amenorrheic; 38% vs. 57% (P = 0.03) and 18% vs. 32% (P = 0.17), respectively. Similar trends were observed within treatment groups. The effect of induced amenorrhoea on outcome was seen predominantly in patients under 40 years old. These results suggest that the induction of ovarian failure is a potential mechanism for the observed effect of adjuvant chemotherapy in these patients. The difference in the ovarian failure rates between groups may be a possible explanation for the inferiority of the 12 week regimen.

Adult↗