Plasma and tissue disposition of non-liposomal DB-67 and liposomal DB-67 in C.B-17 SCID mice.

PURPOSE: DB-67 is a silatecan, 7-silyl-modified camptothecin, with enhanced lipophilicity and increased blood stability of the active-lactone ring. The generation of a liposomal formulation of DB-67 may be an attractive method of intravenous (IV) administration and may maintain DB-67 in the active-lactone form. We evaluated the tissue and plasma disposition of DB-67 lactone and hydroxy acid after administration of non-liposomal (NL) and liposomal (L) DB-67 in severe combined immunodeficient (SCID) mice. METHODS: NL-DB-67 and L-DB-67 10 mg/kg IV x 1 were administered via a tail vein in SCID mice. After dosing, mice (n = 3 per time point) were euthanized and blood ( approximately 1 ml) and tissue were collected from 5 min to 48 h after administration. DB-67 lactone and hydroxy acid concentrations in plasma and DB-67 total (sum of lactone and hydroxyl acid) concentrations in tissues were determined by high-performance liquid chromatography (HPLC) with fluorescence detection. RESULTS: Clearance of DB-67 lactone after administration of NL-DB-67 and L-DB-67 were 1.6 and 3.5 l/h/m(2), respectively; DB-67 lactone half-lives after administration of NL-DB-67 and L-DB-67 were 1.4 and 0.9 h, respectively. The percentages of DB-67 lactone in plasma after administration of NL-DB-67 and L-DB-67 were 92% and 89%, respectively. Liver, kidney, spleen, and lung tissues had longer exposure times to DB-67 after administration of L-DB-67 compared with NL-DB-67. CONCLUSION: In plasma, the majority of DB-67 remained in the lactone form after administration of NL-DB-67 and L-DB-67. The plasma disposition of DB-67 was similar after administration of NL-DB-67 and L-DB-67, suggesting that most of the DB-67 is immediately released from the L-DB-67 formulation. Following administration of L-DB-67, the higher and longer exposure of DB-67 in the spleen, as compared with NL-DB-67, is consistent with splenic clearance of liposomes by the reticuloendothelial system.

Managing bone loss in men with locally advanced prostate cancer receiving androgen deprivation therapy.

PURPOSE: We reviewed the pathogenesis, diagnosis, prevalence, prevention and treatment of bone loss in patients with nonmetastatic prostate cancer receiving androgen deprivation therapy. MATERIALS AND METHODS: Using PubMed we performed a comprehensive literature search to identify articles on bone mineral density loss in patients with nonmetastatic prostate cancer receiving androgen deprivation therapy. Pertinent articles were reviewed and evaluated. RESULTS: Bone mineral density loss and related fractures were recently established as significant adverse events associated with androgen deprivation therapy. Patients with nonmetastatic prostate cancer receiving androgen deprivation therapy experience annual bone mineral density losses of 0.6% to 4.6% with the most significant loss within year 1 of therapy. In addition to calcium and vitamin D supplements, current treatment options for androgen deprivation therapy induced bone loss include synthetic estrogens, selective estrogen receptor modulators and bisphosphonates. Recent safety concerns have been identified, including renal dysfunction with intravenous bisphosphonates and osteonecrosis of the jaw with oral and intravenous bisphosphonates. However, minimal renal dysfunction and no cases of osteonecrosis of the jaw have been reported in this setting. CONCLUSIONS: Because the most significant bone mineral density loss occurs within year 1 of androgen deprivation therapy and most fractures in healthy men occur in those without osteoporosis, early intervention is warranted to prevent skeletal morbidity in patients with nonmetastatic prostate cancer receiving androgen deprivation therapy. Although the majority of and the most compelling evidence supports the use of bisphosphonates for preventing and treating androgen deprivation therapy induced bone loss, further study is needed to define the optimal regimen, timing of initiation and duration of therapy as well as long-term efficacy and safety.

Disposition of 9-nitrocamptothecin and its 9-aminocamptothecin metabolite in relation to ABC transporter genotypes.

PURPOSE: The source of the pharmacokinetic variability of 9-nitrocamptothecin (9NC) and its 9-aminocamptothecin (9AC) metabolite is unknown. ATP-binding cassette (ABC) transporters have been reported to modulate camptothecin analogues, are associated with camptothecin resistance, and might also affect 9NC and 9AC pharmacokinetics. The aim of this study was to evaluate the functional consequence of known single nucleotide polymorphisms in the transporter genes ABCB1, ABCC2, and ABCG2 on the pharmacokinetic disposition of 9NC and 9AC. EXPERIMENTAL DESIGN: Pharmacokinetic and genotyping studies were performed in 55 patients as part of two phase I studies of 9NC in patients with refractory solid tumors, a phase II study of 9NC in patients with advanced colon cancer, and a study evaluating the disposition of 9NC after administration of a single dose under fasting conditions. DNA was isolated from plasma and analyzed for variants in ABCB1, ABCC2, and ABCG2 genes. The ABCB1 1236C>T (n = 43), ABCB1 2677G>T/A (n = 43), ABCB1 3435C>T (n = 43), ABCC2 3972C>T (n = 39), and ABCG2 421C>A (n = 42) variants were analyzed using Pyrosequencing. RESULTS: The ABCG2 421C>A genotype significantly affected the pharmacokinetics of 9AC. The mean 9AC lactone AUC/dose for wild-type (n = 25) and heterozygous (n = 2) patients were 14.3 ng/mL x h and 51.1 ng/mL x h, respectively (P = 0.032). The mean +/- SD 9AC total AUC/dose for wild-type (n = 39) and heterozygous (n = 3) patients were 91.9 +/- 78.3 ng/mL x h and 129.0 +/- 90.5 ng/mL x h, respectively (P = 0.40). 9NC and 9AC disposition were not significantly influenced by variants in ABCB1, ABCC2, and ABCG2, and ABCB1 and ABCC2, respectively (P > 0.05). CONCLUSION: These findings suggest that inter-individual variability in 9AC disposition, but not 9NC, may be influenced, in part, by ABCG2 genotype. In contrast, there was no evidence for a relationship between ABCG2 and the disposition of 9NC, or for relationships between ABCB1 and ABCC2 genotypes and the disposition of 9NC or 9AC.

Relationship between plasma exposure of 9-nitrocamptothecin and its 9-aminocamptothecin metabolite and antitumor response in mice bearing human colon carcinoma xenografts.

9-Nitrocamptothecin has completed phase III studies in patients with newly diagnosed and refractory pancreatic cancer; however, the optimal 9-nitrocamptothecin treatment regimen is unclear. We used an intermittent schedule of 9-nitrocamptothecin to evaluate the relationship between plasma exposure of 9-nitrocamptothecin and its 9-aminocamptothecin metabolite and antitumor response in mice bearing human colon carcinoma xenografts. 9-Nitrocamptothecin was given orally at 0.44, 0.67, or 1.0 mg/kg/d qd x 5d x 2 weeks repeated q 4 weeks for two cycles to female C.B-17 SCID mice bearing HT29 or ELC2 human colon xenografts. Pharmacokinetic studies were done after oral administration of 0.67 mg/kg x 1. Serial samples were obtained and 9-nitrocamptothecin and 9-aminocamptothecin lactone concentrations in plasma were determined by high-performance liquid chromatography analysis with fluorescence detection. The areas under plasma concentration versus time curve (AUC) from 0 to infinity for 9-nitrocamptothecin and 9-aminocamptothecin were calculated. The antitumor activity of 9-nitrocamptothecin was dose-dependent in both colon xenografts. At all doses, 9-nitrocamptothecin treatment resulted in significant antitumor activity in both xenografts compared with vehicle-treated and control groups and achieved levels of tumor regression that met criteria (minimum %T/C < or = 40%) for antitumor activity. In mice bearing HT29 xenografts, the 9-nitrocamptothecin and 9-aminocamptothecin lactone AUCs after administration of 9-nitrocamptothecin at 0.67 mg/kg were 41.3 and 5.7 ng/mL h, respectively. The responses seen in these xenograft models occurred at systemic exposures that are tolerable in adult patients. These results suggest that the intermittent schedule of 9-nitrocamptothecin may be an active regimen in patients with colorectal carcinoma.

Phase I study of weekly (day 1 and 8) docetaxel in combination with capecitabine in patients with advanced solid malignancies.

PURPOSE: Capecitabine in combination with docetaxel given every 3 weeks has shown a high degree of activity in a number of tumor types, but at the expense of significant toxicity. To improve the therapeutic index, we evaluated a weekly regimen of docetaxel in combination with capecitabine, and determined the maximum tolerated dose, toxicities and pharmacokinetics of this combination. PATIENTS AND METHODS: Patients with advanced solid malignancies were treated with docetaxel on days 1 and 8, and capecitabine, twice daily on days 1-14, of an every-21-day cycle. Pharmacokinetics of docetaxel were assessed on days 1 and 8 of the first cycle of chemotherapy. RESULTS: Enrolled in the study were 25 patients. The most frequent toxicities were asthenia, hand-foot syndrome and mucositis. Inability to deliver at least 75% of the planned doses of both drugs during the first two cycles of chemotherapy was noted at dose levels 2, 3 and 4. Dose level 1 (docetaxel 30 mg/m2 and capecitabine 825 mg/m2 twice daily) is the recommended dose for phase II studies. Five patients experienced a partial response, and eight patients had stabilization of disease. Coadministration of capecitabine did not alter the pharmacokinetics of docetaxel. CONCLUSION: The regimen consisting of docetaxel 30 mg/m2 (days 1, 8) and capecitabine 825 mg/m2 twice daily (days 1-14) was well tolerated. Capecitabine did not alter pharmacokinetics of docetaxel. Further testing of this regimen in tumor-specific trials, especially gastric, lung and breast cancer, is warranted.

Phase I and pharmacologic study of intermittently administered 9-nitrocamptothecin in patients with advanced solid tumors.

PURPOSE: 9-Nitrocamptothecin (9NC) is an oral camptothecin analogue currently administered at 1.5 mg/m(2)/day x 5 days/week in Phase III studies for pancreatic carcinoma. In an effort to increase the dose administered per day and determine whether the daily dose or number of days of treatment influence toxicity, we performed a Phase I study of 9NC using intermittent schedules of administration. EXPERIMENTAL DESIGN: On schedule A, 9NC was administered orally daily x 5 days for 2 weeks every 4 weeks (one cycle). On schedule B, 9NC was administered orally daily x 14 days every 4 weeks (one cycle). Dose levels were determined by adaptive dose finding. Serial blood samples were obtained on day 1 of each schedule for pharmacokinetic studies of 9NC and its 9-aminocamptothecin (9AC) metabolite, and lactone forms were measured by high-performance liquid chromatography. RESULTS: The recommended Phase II doses for schedules A and B were 2.43 and 1.70 mg/m(2)/day, respectively, each providing the same dose intensity (i.e., 24 mg/m(2)/cycle). The primary toxicities on schedules A and B were neutropenia, thrombocytopenia, and diarrhea. On schedule A, two patients with gastric cancer and two patients with pancreatic cancer had stable disease for more than six cycles. On schedule B, one patient with pancreatic cancer had stable disease for more than six cycles, and a patient with pancreatic cancer had a partial response. There was significant interpatient variability in the disposition of 9NC and 9AC. Most of the drug remained in the 9NC form with a ratio of 9NC to 9AC of approximately 4 to 1. CONCLUSIONS: These studies suggest that 9NC administered on an intermittent schedule is tolerable and may be an active regimen in patients with gastric or pancreatic cancers. Dosing 9NC on a mg/m(2) basis does not reduce pharmacokinetic variability.

Pharmacokinetic studies of 9-nitrocamptothecin on intermittent and continuous schedules of administration in patients with solid tumors.

PURPOSE: Oral administration of 9-nitrocamptothecin (9NC), and the formation of its metabolite 9-aminocamptothecin (9AC), may be associated with high interpatient and intrapatient variability. Therefore, we evaluated the plasma pharmacokinetics and urine recovery of 9NC administered on three different schedules as part of phase I and phase II studies. EXPERIMENTAL DESIGN: In phase I schedule A, 9NC was administered orally daily for 5 days per week for 2 weeks repeated every 4 weeks. On phase I schedule B, 9NC was administered daily for 14 days repeated every 4 weeks. In Phase II, 9NC was administered daily for 5 days during 8 weeks (one cycle). Serial blood samples were obtained on day 1 and day 10 or 11 for phase I studies, and day 1 and day 50 for the phase II study. Recovery of 9NC and 9AC in urine was evaluated on day 1 and day 10 or 11 in the phase I study. Area under the 9NC and 9AC plasma concentration vs time curves from 0 to 24 h (AUC0-24 h) were calculated using compartmental analysis. RESULTS: The mean+/-SD 9NC lactone AUC0-24 h values on day 1 at the maximum tolerated dose of schedules A and B (2.43 and 1.70 mg/m2, respectively) and the phase II dose (1.5 mg/m2) were 78.9+/-54.4, 155.7+/-112.8, and 48.3+/-17.5 ng/ml.h, respectively. The mean+/-SD 9AC lactone AUC0-24 h values at these same doses of 9NC were 17.3+/-17.9, 41.3+/-16.6, and 31.3+/-12.8 ng/ml h, respectively. The ratios of 9NC lactone AUC0-24 h on day 10 or 11 to day 1 on phase I A and B were 1.27+/-0.68 and 1.73+/-1.56, respectively, and the ratios 9AC lactone AUC0-24 h on day 10 or 11 to day 1 on phase I A and B were 2.23+/-1.02 and 1.65+/-0.97, respectively. The recovery of 9NC and 9AC in the urine was <15%. CONCLUSIONS: There was significant interpatient and intrapatient variability in the disposition of 9NC and 9AC. 9NC and 9AC undergo primarily nonrenal elimination.