Phase I and pharmacokinetic study of 7-hydroxystaurosporine and carboplatin in advanced solid tumors.

PURPOSE: Based on preclinical data showing synergy between 7-hydroxystaurosporine (UCN-01) and platinum agents, a phase I trial of carboplatin with UCN-01 administered as a 3 h infusion in patients with advanced solid tumors was done. The primary goals of this trial were to evaluate the tolerability of this combination and the pharmacokinetics of UCN-01 when administered over 3 h and to compare the tolerability and pharmacokinetics with previously described schedules. PATIENTS AND METHODS: Patients with advanced solid tumors, good performance status, normal organ function, and no potentially curative therapy were eligible for the trial. Carboplatin was escalated from an area under the curve (AUC) of 3 to an AUC of 5. UCN-01 was escalated from 50 to 90 mg/m(2). RESULTS: Twenty-three patients with advanced solid tumors (20 with prior platinum treatment) received a total of 60 cycles of therapy. Full doses of both agents (carboplatin AUC 5, UCN-01 90 mg/m(2) in cycle 1, 45 mg/m(2) in subsequent cycles) could be administered. The major toxicity noted was hypotension, which could be abrogated with the use of saline prehydration and posthydration. No responses were seen; however, seven patients were able to receive more than two courses of therapy. Of note, two of three patients with refractory, progressive small cell lung cancer were able to receive six cycles of therapy without evidence of progression. One patient experienced resolution of paraneoplastic syndrome of inappropriate antidiuretic hormone. The pharmacokinetic variables C(max) and t(1/2) of the 3 h infusion were essentially identical to those previously observed when UCN-01 was administered over 72 h. The average t(1/2) for cycle 1 was 506 +/- 301 h, and the mean C(max) for all dose levels was >30 micromol/L. The mean AUC over the dosing interval for each dose level ranged from approximately 6,000 to 9,000 micromol/L h. Thus, the AUC of UCN-01 after the 3 h infusion was lower than was observed after a 72 h infusion. CONCLUSION: The regimen of carboplatin and UCN-01 (administered as a 3 h infusion) was well tolerated. Further development of this combination, particularly in small cell lung cancer, is warranted.

IMP dehydrogenase inhibitor mycophenolate mofetil induces caspase-dependent apoptosis and cell cycle inhibition in multiple myeloma cells.

Multiple myeloma is an incurable disease for the majority of patients, therefore requiring new biological targeted therapies. In primary myeloma cells, IMP dehydrogenase (IMPDH) was shown to be consistently overexpressed. We therefore tested the IMPDH inhibitor mycophenolate mofetil (MMF) currently available as a clinical therapeutic agent for its antimyeloma activity in vitro. MMF depleted intracellular guanosine 5'-triphosphate (GTP) levels in myeloma cells. We showed apoptosis induction in myeloma cell lines and primary myeloma cells between 1 and 5 mumol/L MMF. MMF was also cytotoxic at this concentration in dexamethasone-resistant and Mcl-1-overexpressed myeloma cell lines shown by the tetrazolium salt XTT assay along with cell survival measured by a modified flow cytometric assay. Apoptosis was not inhibited by the presence of an antioxidant, suggesting that MMF-induced apoptosis is less likely to be associated with reactive oxygen species. However, apoptosis was abrogated by exogenously added guanosine, which activates an alternative pathway for GTP formation, implicating that this effect is directly mediated by IMPDH inhibition. MMF-induced G1-S phase cell cycle arrest and its apoptosis induction mechanism were associated with a caspase-dependent pathway as shown by alteration of mitochondrial membrane potential and cytochrome c release followed by activation of the caspases. MMF-induced apoptosis was also inhibited by a pan-caspase inhibitor Z-VAD-fmk. MMF-treated myeloma cells showed an up-regulation of Bak, which most likely together with Bax resulted in the release of cytochrome c. In summary, MMF attenuates G1-S phase cell cycle progression and activates the pathway of mitochondrial dysfunction, leading to cytochrome c release followed by activation of caspases.

A phase I and pharmacologic study of idarubicin, cytarabine, etoposide, and the multidrug resistance protein (MDR1/Pgp) inhibitor PSC-833 in patients with refractory leukemia.

This study was conducted to define the maximum tolerated dose (MTD), dose limiting toxicity (DLT), and pharmacokinetics of idarubicin when administered with and without the P-glycoprotein inhibitor PSC-833 in combination with cytarabine, and etoposide. Fifteen patients with relapsed and refractory acute leukemia were enrolled and received cytarabine as a 7-day continuous infusion, with etoposide and idarubicin administered for any three consecutive days during the cytarabine infusion. Two hours prior to the second dose of idarubicin, PSC-833 administration was initiated. The pharmacokinetics of idarubicin alone and with PSC-833 was assessed at three idarubicin dose levels (6, 8 and 10 mg/m(2)). The MTD of idarubicin in this combination was 8 mg/(m(2) day) with a DLT of oral mucositis. The complete remission rate (on an intent-to-treat basis) for this regimen was 33%, with a median duration of 6 months. The clearance of idarubicin was 140 +/- 200 and 181 +/- 94.3 l/h for idarubicin alone and with PSC-833, respectively. The volume of distribution of the central compartment was 423 +/- 443 and 337 +/- 394 l for idarubicin alone and in combination with PSC-833, respectively. This combination including PSC-833 was well tolerated. Although a pharmacokinetic interaction might have been expected, PSC-833 did not significantly alter the disposition of idarubicin.

Phase I clinical trial of the inosine monophosphate dehydrogenase inhibitor mycophenolate mofetil (cellcept) in advanced multiple myeloma patients.

PURPOSE: Inosine monophosphate dehydrogenase (IMPDH) inhibitors have been used to induce leukemia blast cell differentiation but have not been tested in multiple myeloma for activity. Currently, available IMPDH inhibitor, mycophenolate mofetil (MMF), which is known as an immunosuppressant, was shown to induce apoptosis in myeloma cell lines. On the basis of our preclinical studies, we designed a clinical study to test our hypothesis that MMF has antimyeloma activity. EXPERIMENTAL DESIGN: A Phase I MMF dose escalation study was conducted in relapsed and refractory myeloma patients who had documented disease progression by myeloma markers or bone marrow plasmacytosis to determine the maximum tolerated dose, toxicities, and efficacy of the drug. To assess the activity of IMPDH inhibition in the myeloma cells of patients, we measured intracellular nucleotide triphosphate levels by high-performance liquid chromatography-based analysis and examined the correlation with clinical response. RESULTS: Among the 11 study patients, MMF was generally well tolerated and was administered up to a maximum dose of 5 g/day. The most common toxicity was grade 1 fatigue (n = 4, 36%). One patient had a partial response (3 g/day), four patients had stable disease, and six patients had progression of disease. There was a statistically significant difference in the intracellular dGTP level changes between the stable disease/partial response group versus progression of disease. CONCLUSIONS: MMF at 1 to 5 g/day daily dose is well tolerated by patients with relapsed and refractory multiple myeloma patients. Positive correlation between clinical response and depletion of intracellular dGTP level was shown. Future drug development to target this enzyme maybe useful in treating myelomas.

Functional characterization of human breast cancer resistance protein (BCRP, ABCG2) expressed in the oocytes of Xenopus laevis.

To evaluate the function and substrate specificity of human breast cancer resistance protein (BCRP, ABCG2) in the absence of cofactors or heterologous partner proteins, Xenopus laevis oocytes were injected with cRNA of wild-type or mutant (R482T) BCRP. High expression of BCRP was observed on the oocyte surface. Accumulation and efflux assays revealed that oocytes expressing R482T transported daunorubicin (DNR), mitoxantrone (MX), rhodamine 123, and flavopiridol (FLV), whereas wild-type BCRP transported only MX and FLV, in agreement with observations in mammalian and other systems. Transport activity was completely inhibited by fumitremorgin C, a known inhibitor of BCRP. Injection of oocytes with cRNA containing mutations of serine 187 in the ATP-binding cassette signature motif (S187T or S187A) resulted in strong expression of the mutant forms; however, these oocytes were devoid of transporter activity. When oocytes were coinjected with R482T and R482T/S187T, DNR transport was inhibited in a manner dependent on the amount of R482T/S187T cRNA added, consistent with the idea that the active form of BCRP is a homodimer or homomultimer. Substrate interaction studies found that no two substrates reciprocally inhibited the efflux of the other. Although FLV proved to be an effective inhibitor of both MX and DNR transport, and MX inhibited DNR transport, the other substrates tested had only weak or no inhibitory activity, indicating a complex nature of substrate interaction with the BCRP homodimer. We conclude that the X. laevis oocyte heterologous expression system is a valid and effective means of studying BCRP function and substrate specificity.