A phase I study of XL281, a selective oral RAF kinase inhibitor, in patients (Pts) with advanced solid tumors

3513

Background: XL281 is a potent and selective inhibitor of wild type and mutant RAF kinases showing anti-tumor activity in multiple xenograft models. Mutations in KRAS or BRAF can activate the RAF/MEK/ERK pathway in human tumors and may promote sensitivity to RAF kinase inhibitors. Methods: Pts were enrolled in successive cohorts of XL281 orally once daily on a 28-day cycle. Tumor response was assessed per RECIST every 8 wks. Plasma pharmacokinetic and pharmacodynamic samples were collected. The maximum tolerated dose (MTD) was expanded to 10 pts each with colorectal (CRC), melanoma, papillary thyroid (PTC) and NSCLC. Pre- and post-dose tumor and surrogate tissues were obtained. Biomarker and genotype analyses of pathway genes were performed. Results: The dose escalation phase is complete; 30 pts were treated with XL281. DLTs of fatigue, nausea, vomiting, and diarrhea were observed at the MAD (225 mg). The MTD is 150 mg. The most common related AEs included Grade 1/2, fatigue (48%), diarrhea (35%), nausea (35%), vomiting (35%) and anorexia (30%). Three pts had related AEs ≥G3: hypokalemia, nausea, and vomiting. One pt with an ocular melanoma demonstrated a cPR of 4 mos duration. Twelve pts had SD (3 -17+ mos), including 2 with I131-refractory PTC harboring BRAF V600E mutations (15+ and 17+ mos). Nine of these pts had decreases in target lesions (5–29%), including a pt with KRAS mutant CRC on study for 20 wks with marked symptomatic improvement. At the MTD, paired biopsies from 4 pts (3 melanoma, 1 NSCLC) show an average 72 % decrease in pMEK, 68 % decrease in pERK, 24 % decrease in Ki67 (proliferation) and 64 % increase in TUNEL (apoptosis). Three of 6 evaluable pts in the MTD cohort show SD at first assessment, including 1 melanoma pt with a NRAS Q61R mutation who showed a 20% decrease in target lesions. Conclusions: XL281 was generally well tolerated and the MTD was established at 150 mg. One cPR occurred in an ocular melanoma subject, and clinical benefit (PR or SD) occurred in 43% (13/30) of pts in the dose-escalation phase. XL281 demonstrates biological activity by modulation of the RAF pathway in tumor and surrogate tissue, with decreases in cell proliferation and increases in apoptosis.

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A phase I clinical trial of FOLFIRI in combination with the pancyclin–dependentkinase (CDK) inhibitor flavopiridol

e14511

Background: Preclinical data indicate that sequential treatment with flavopiridol (F) increases irinotecan- and 5-FU-induced apoptosis. Clinically, F showed promising activity when combined with irinotecan (Shah et al CCR 2005). Methods: We conducted a phase I trial of FOLFIRI + F every 2 weeks in patients (pts) with advanced solid tumors. Based on sequence- dependent inhibition, F was given 3 h after irinotecan but before 5-FU. Two maximum tolerated doses (MTD) were determined: MTD1 (F over 1 h) and MTD2 (F 30-min bolus + 4 h infusion). F pharmacokinetics (PK) were determined. Results: Of 74 pts treated, 63 were evaluable for toxicity and 56 for response. Pt characteristics: median age 60 (range 19–83), KPS 90 (70–90), prior regimens 3 (1–10). 39 pts received prior irinotecan. Tumor types: colorectal, gastric, HCC, GE junction, small bowel, pancreas, bile duct, breast, bladder, ovarian, sarcoma, melanoma, anal, urethral, thymic, head & neck, unknown primary. MTD1: F 80mg/ m2 with irinotecan 180mg/m2, LV 400mg/m2, 5FU: 400mg/m2 bolus + 2400mg/m2 over 48 h. Dose-limiting toxicities (DLT) were diarrhea, fatigue, neutropenia, neuropathy. MTD2: F 35mg/m2 bolus + 35mg/m2 over 4 h with the same FOLFIRI dose. DLTs were diarrhea, neutropenia, and fatigue. Clinical activity included 2 partial responses (small bowel cancer, 10.3 m; bladder cancer, 10 m) and 1 complete response (mucosal melanoma 10.3 m). 22 pts had stable disease (median 5.9 m; range 1.5–25.7 m). Clinical benefit rate (CR + PR + SD for > 3 m) was 39% (22/56). Of 25 pts with colorectal cancer, 11 had as best response SD for > 3m (median 6 m, range 4.2–15.4 m), despite failing ≥ 1 irinotecan-containing regimen. 6 of those had significant decreases (36–78%) in CEA. F PK showed interpatient variability with no significant interaction between FOLFIRI dose and F Cmax. F Cmax increased with increasing F dose. At MTDs, there was higher Cmax in pts who experienced DLT (3.48μM) vs those who did not (2.21μM). Conclusions: F can be safely given as a bolus (80mg/m2) or split dose (35mg/m2 bolus + 35mg/ m2 over 4 h) in combination with irinotecan 180mg/m2, LV 400mg/m2, 5FU: 400mg/m2 bolus + 2400mg/m2 over 48 h. Promising clinical activity is seen in mucosal melanoma and irinotecan-refractory colon cancer. (Supported by NCI R01CA67819)

[Table: see text]

A phase I dose escalation trial of a daily oral CDK 4/6 inhibitor PD-0332991

3550

Background: PD-0332991 is a novel oral inhibitor of CDK 4/6, which is active against Rb positive tumors and has never before been tested in humans. A phase I dose escalation trial of PD-0332991 administered as a daily oral single agent was conducted to investigate safety, pharmacokinetics and pharmacodynamics in patients with advanced cancer. Methods: PD-0332991 was administered daily for 21 days in 28-day cycles (Schedule 3/1) to patients in successive dose escalating cohorts at doses from 25 mg to 150 mg QD. An alternative schedule of 14 days dosing in 21-day cycles (Schedule 2/1) was tested at 100 mg to 225 mg QD. Patients with advanced Rb positive solid tumors were enrolled in the study. Results: Fifty-seven patients have been enrolled into the study. The most common tumor types were: breast, colorectal, liposarcoma, and melanoma. The median age across the study was 57 years. For Schedule 3/1, the MTD/RP2D was determined to be 125 mg QD. For Schedule 2/1, the MTD/RP2D is still to be identified but the maximum administered dose (MAD) was determined to be 225 mg QD. Six DLTs have been observed, all relating to myelosuppression. The most common AEs were neutropenia, anemia, fatigue, nausea, constipation, vomiting and diarrhea. Concentrations were moderately variable (% CV range in AUC on Day 8 of Cycle 1 was 14–64%) with dose-dependent increases in exposure observed following PD-0332991 administration (mean AUC(0–10 hr) values were 724 and 1,500 ng.hr/mL at the 125 mg and 225 mg dose levels, respectively). The effect of food on PD-0332991 pharmacokinetics is currently being evaluated. In Schedule 3/1, there have been 6 patients with stable disease (= 10 cycles) with 3 patients (one each with breast cancer, colon cancer and ovarian cancer) with stable disease for at least 20 cycles. In Schedule 2/1, one patient has had stable disease for at least 10 cycles. Updated data will be presented. Conclusions: The principal and dose limiting toxicity of PD- 0332991 is myelosuppression. The RP2D for Schedule 3/1 is 125 mg QD. The MAD has been determined for Schedule 2/1 as 225 mg QD and the dose in this schedule has been de-escalated to 200 mg QD to evaluate the MTD. Tumor specimens, when available, from patients in both schedules are also being tested for pharmacodynamic modulation of phospho-RB protein.

No significant financial relationships to disclose.

Phase 1 dose-escalation study of 17-allylamino-17-demethoxygeldanamycin (17AAG) in combination with irinotecan in patients with solid tumors

3533

Background: 17AAG is an inhibitor of the molecular chaperone Hsp90. Pre-clinical studies from our laboratory showed that treatment of cancer cells with 17AAG caused depletion of two critical checkpoint kinases, Chk1 and Wee1, resulting in abrogation of the G2/M checkpoint triggered by topoisomerase I poison, and selective induction of apoptosis in p53-defective cells. Methods: We initiated a phase 1 study of irinotecan (CPT) and 17AAG to determine the maximally tolerated doses (MTD) and tolerability, pharmacokinetics (PK) and pharmacodynamics (PD) of the combination. During the dose-escalating phase, patients (Pts) received CPT over 30 min followed by 17AAG over 2 hrs once weekly for two weeks in a 21-day cycle. At the MTD, Pts underwent post-treatment tumor biopsy for PD biomarker analysis after CPT only during week 1 and after the combination during week 2. Results: 22 Pts (median age 53; range 32–73; median KPS 80) with a wide spectrum of solid tumor types were enrolled. Four Pts developed dose-limiting toxicity in cohort 4 (100 mg/m2 CPT and 375 mg/m2 17AAG) including nausea, vomiting, diarrhea, and pulmonary embolism. The PKs of 17AAG and its metabolite 17AG were not affected by the co-administration of CPT. Although no CR/PR’s by RECIST criteria have been seen, minor responses were observed in CPT-naive Pts with pancreas (2), breast (1), and high grade neuroendocrine tumor (1). Pts are currently enrolled to the MTD expanded cohort for further assessment of tolerability and PD analysis. So far, paired tumor biopsies have been successfully obtained in 8/8 Pts and samples will be analyzed for p53 status, Hsp90 client protein depletion, G2/M checkpoint abrogation, and apoptosis. Conclusions: The combination of 17AAG and CPT can be given to Pts with acceptable toxicity. The recommended phase II dose of the combination is 100 mg/m2 CPT and 300 mg/m2 17AAG. (Supported by ASCO CDA and NCI K08 awards)

No significant financial relationships to disclose.

Pharmacokinetics (PK) of split-dose flavopiridol (F) administered with CPT-11 (CPT) and cisplatin (Cis)

2578

Background: F, a cyclin-dependent kinase inhibitor, induces tumor lysis in CLL when administered as a 30 mg/m2 loading dose over 0.5h followed by a 30 mg/m2 maintenance dose over 4h (hybrid F; Byrd et al, Blood 2006). F given as a 1h bolus (bolus F) demonstrates promising clinical activity when combined with CPT in solid tumors (Shah et al, CCR 2005). Data suggest that F concentrations of 2–3 μM are required to enhance the effects of CPT in solid tumors (Motwani et al, CCR 2001), but controversy exists over the optimal F schedule for chemotherapy potentiation. Methods: We are conducting a phase I trial of CPT/Cis→F, with F administered on both a bolus F and hybrid F schedule. After identifying the maximum tolerated dose (MTD) of bolus F (CPT/Cis→F 50mg/m2), the hybrid F schedule was examined. The F loading dose was escalated from 20→30mg/m2 and the F maintenance dose escalated from 20→50mg/m2. Plasma samples were obtained from patients (pts) treated with bolus F at the MTD and with hybrid F at all dose levels. To better assess F PK interaction with CPT/Cis, F was given before CPT/Cis on cycle 2 only. Results: Complete PK data are available from 6 pts treated at the bolus F MTD (50 mg/m2) and on 20 pts treated with hybrid F (20→20 mg/m2, 25→25 mg/m2 and 30→30 mg/m2) for cycles 1 and 2. Both bolus F and hybrid F PK are consistent with data previously reported. Although cycle 1 AUCs are similar for bolus F 50 mg/m2 and hybrid F 30→30 mg/m2 (10.47±4.97 vs 10.75±15.14 μM/h, p=NS), the Cmax achieved with bolus F 50 mg/m2 is significantly greater than that achieved with hybrid F 30→30 mg/m2 (2.31±0.65 vs 1.21±0.35 μM, p<0.02). No significant PK differences occurred between cycles 1 and 2. Toxicity was not associated with F Cmax. With CPT/Cis→bolus F, the PR rate was 10/29 (35%) vs 3/33 (9%) with CPT/Cis→hybrid F. Conclusions: The Cmax achieved with bolus F is greater than that achieved with hybrid F, with no increase in toxicity. Additionally, the Cmax achieved with hybrid F does not exceed the 2 μM plasma concentration required for potentiation of chemotherapy-induced apoptosis. The greater number of responses achieved with bolus F suggests that bolus F may be more efficacious than hybrid F when used in combination with CPT for the treatment of solid tumors. (Supported by R01-CA67819)

No significant financial relationships to disclose.

A phase I clinical study of safingol followed by cisplatin: promising activity in refractory adrenocortical cancer with novel pharmacology

13044

Background: Safingol (L-threo-dihydrosphingosine), originally identified as a competitive inhibitor of protein kinase C, has been re-identified as an inhibitor of sphingosine kinase (SK). Inhibition of SK induces apotosis and autophagy by increasing intracellular conversion of sphingosine to ceramide. In vivo, safingol enhances the antitumor activity of cisplatin in a sequence dependent manner (safingol→cisplatin). Methods: We designed a phase I trial of escalating doses of safingol (60→120→240→ 360→480→600 mg/m2) followed 1 hr later by fixed-dose cisplatin 75 mg/m2 given q21 days in pts with advanced solid tumors. Standard phase I eligibility critieria apply. Prior cisplatin is allowed. Results: 13 evaluable pts have been enrolled: 5 male/8 female, median age 54 (range 36–68), median KPS 90% (range 80–100%), mean number of priors 2.8 (range 1–6). 2 dose limiting toxicities (DLT) were observed with escalation of safingol to 240 mg/m2 (gr 3 fatigue, gr 3 hyponatremia), both felt to be due primarily to cisplatin. The protocol was amended to reduce cisplatin to 60 mg/m2, given with 240 mg/m2 of safingol. We observed 1 DLT (persistent gr 3 thrombocytopenia) at this dose level. Pharmacokinetic (PK) analysis by mass spectroscopy shows nearly complete clearance of safingol from circulation within 24 hours of treatment with a 10-fold greater amount of safingol in whole blood than in plasma. An increase in sphingosine and dihydroceramide levels were observed with therapy, and N-acyl- and N-methyl- metabolites of safingol were detected. We observed 1 PR (4+ months) in a pt with cisplatin-refractory adrenocortical cancer metastatic to the liver and lung after only 1 cycle of therapy. 1 additional pt with adrenocortical cancer has SD (2+ months) on therapy. Conclusions: Escalating doses of safingol can be safely administered with a fixed dose of cisplatin. PK data reveal acyl- and methyl-safingol for the first time in human plasma, with a significant fraction of safingol bound to human blood cells. We observed unusual activity in pts with adrenocortical cancer. Further dose escalation of safingol with cisplatin 60 mg/m2 is ongoing, and additional PK data and complete sphingolipid profiles will be presented. (Supported by NCI R21-CA112910).

No significant financial relationships to disclose.

A phase I clinical and pharmacokinetic study of flavopiridol administered concurrently with 5-fluorouracil, leucovorin, and oxaliplatin (FOLFOX) for advanced solid tumors

13515

Background: Flavopiridol, a potent cyclin-dependent kinase inhibitor, enhances oxaliplatin-induced apoptosis in HCT116 colon cancer cells in vitro, especially with concurrent therapy. Significant tumor regressions were also observed in HCT116 xenografts treated with flavopiridol and oxaliplatin therapy versus either therapy alone. Methods: Therefore, an ongoing phase I trial in advanced solid tumors was designed in which flavopiridol at a fixed dose (40 mg/m2 over 1 hour) was administered concurrently with escalating doses of oxaliplatin (60 mg/m2 -> 80 mg/m2 over 2 hours), given as part of a modified FOLFOX6 regimen at standard doses every 14 days. Patients then received escalating doses of infusional 5-fluorouracil over 48 hours (900 mg/m2/day -> 1200 mg/m2/day). Standard phase I eligibility criteria apply. Prior FOLFOX or oxaliplatin was allowed. Results: Median characteristics of nineteen evaluable patients: age 54 (39–77), KPS 80% (70–90), 9 males/10 females, 3 prior regimens (range 1 to 10). The combination has been well-tolerated, with 1 dose limiting toxicity occurring with oxaliplatin at 85 mg/m2 and infusional 5-fluorouracil at 1200 mg/m2/day (grade 3 hyponatremia and grade 3 syncope). Pharmacokinetic studies for flavopiridol indicate no appreciable difference in Cmax despite escalation of oxaliplatin dose. We have observed 1 partial response to treatment in pancreatic cancer. Stable disease has been seen in 5 patients, including 1 breast cancer (3 months), 1 gastric cancer (2 months), 1 anal cancer (7 months) and 2 colorectal cancers (5+ months), with one patient previously treated with oxaliplatin. Conclusions: The combination of flavopiridol and modified FOLFOX6 can be given safely without a significant increase in toxicity. The pharmacokinetic data for flavopiridol remains unchanged despite escalating doses of oxaliplatin. Activity has been observed in several tumor types, with promising activity noted for colorectal cancers even with prior oxaliplatin chemotherapy. Therefore, further dose escalation of flavopiridol is currently planned.

No significant financial relationships to disclose.