Population pharmacokinetic (PK) analysis of ABT-869 in solid tumors and acute myelogenous leukemia (AML) patients

3567

Background: ABT-869 is an orally bioavailable, potent and specific inhibitor of all vascular endothelial growth factor and platelet derived growth factor family receptor tyrosine kinases. The objectives of this analysis were to understand the population pharmacokinetics of ABT-869 and explore the effect of several demographic/disease state covariates influencing ABT-869 disposition. Methods: A population PK analysis of 181 patients (pts) enrolled in two phase 1 (multiple types of solid tumors and AML) and three phase 2 monotherapy studies (non-small cell lung cancer, hepatocellular carcinoma [HCC] and renal cell carcinoma) was conducted. Approximately 90% of pts received ABT-869 based on body-weight dosing while the remaining pts had flat dosing. Available plasma concentrations obtained after intensive and sparse pre-dose PK sampling were analyzed by population PK using the non linear mixed effects modeling (NONMEM) approach. Potential covariates including body weight, body surface area (BSA), age, sex, creatinine clearance (CrCL) and disease state (HCC vs. non-HCC pts) were tested. Results: The mean body weight of enrolled pts was 71 kg and 57% were Asian, 36% Caucasian and 7% other races. The ABT-869 plasma concentration time profile was well described by a one-compartment model with first order absorption and elimination process. Oral clearance (CL/F) was not affected by body weight (range 35–177 kg); however, apparent volume of distribution (V/F) increased by 6L per 0.1 mg/m2 increase in BSA. CrCL (39.9–290.3 ml/min) was not a significant covariate on V/F and CL/F suggesting renally impaired pts do not require a different dose/dosing regimen. HCC pts had ∼40% lower CL/F values than pts with other malignancies suggesting a lower dose would be appropriate for HCC (Child Pugh A and B) pts. Conclusions: Population PK analysis showed that ABT-869 PK can be well described by a one-compartment model with first order absorption and elimination. Race and impaired renal function does not appear to alter PK. HCC pts had lower CL/F value therefore a lower dose may be recommended in these patients. Implications of increased V/F with increasing body size and appropriate dosing strategy are undergoing further analysis.

[Table: see text]

ABT-263 activity and safety in patients with relapsed or refractory lymphoid malignancies in particular chronic lymphocytic leukemia (CLL)/small lymphocytic lymphoma (SLL)

8574

Background: ABT-263, a novel, orally bioavailable, BH3 mimetic, binds with high affinity (Ki ≤ 1nM) and inhibits multiple antiapoptotic Bcl-2 family proteins. ABT-263 displays activity (EC50 ≤ 1μM) against human lymphoid and small cell lung cancer cell lines. Mechanism based preclinical toxicities include reductions in circulating lymphocytes, apoptosis of circulating platelets, and decreased spermatogenesis, mediated by inhibition of Bcl-2, Bcl-XL, and Bcl-w, respectively. Methods: Safety and activity of ABT-263 in 2 enrolling phase I studies in relapsed/refractory lymphoid malignancies (M06–814) and CLL (M06–873) was evaluated. Patients (pts) were dosed on days 1–14 of a 21 d cycle, 10–440mg (M06–814) or 10–250mg (M06–873). Continuous 21/21 d dosing (CD) post lead-in dose is being explored in both studies. Results: 55 pts, 14/21 d dosing, enrolled in the 2 studies. ABT-263 PK were linear from 10 - 440mg (N=55) and the terminal half-life was 14 - 20 h (n=35). Among 27 CLL/SLL pts, 3 have confirmed radiographic partial responses (PR) (99%, 92% and 72%) and 2 have unconfirmed regressions, 51% and 72%. 6 pts maintained a ≥50% decrease in circulating lymphocytes for ≥ 2 months and 11 pts have stable disease; of these 5 experienced minor radiographic responses (range of 36% to 49%). In addition, among 40 (M06–814) lymphoma pts, 3 with follicular lymphoma achieved PR and one had a minor response (49% regression). With CD dosing (16 pts), activity includes 1 unconfirmed PR in SLL & and 3 CLL pts with ≥50% lymphocyte reduction for ≥2 months duration. Pharmacodynamic toxicities included dose-dependent thrombocytopenia (TCP) resulting from on-target activity against Bcl-XL. Dose limiting toxicities, 14/21 d dosing, in M06–814 occurred at 160mg (bronchitis), 315mg (elevated ALT and grade 4 TCP) and 440mg (worsening pleural effusion in a pt with underlying afib), and in M06–873 at 110mg (tumor lysis and grade 4 TCP) and 250mg (grade 4 TCP). Conclusions: ABT-263 showed favorable PK and safety profiles with anti-tumor activity in relapsed/refractory CLL/SLL and follicular lymphoma. Identification of optimal dose and schedule for phase II trials continues.

[Table: see text]

Phase I and biomarker study of ABT869, a multiple receptor tyrosine kinase inhibitor, in patients with refractory solid malignancies

3519

Background: ABT869 is an orally administered, potent and specific inhibitor of all VEGF and PDGF family tyrosine kinases, including FLT-3, and c-kit receptors. Methods: A phase I study of ABT869 in patients with refractory solid malignancies was initiated to determine the maximum tolerable dose (MTD) of ABT869 given by continuous once-daily oral dosing; evaluate ABT869 pharmacokinetics; assess pharmacodynamic effects on plasma VEGF and circulating endothelial cells (CECs); evaluate tumor response, including an assessment of microcirculatory parameters DCE-MRI. Dose escalation was planned in dose cohorts of 3 patients each. Treatment periods (TP) were defined as 21 days and tumor assessments were performed using CT scans every 6 weeks. DCE-MRI was done at baseline, day 3 and 14 of the first cycle. Cohort expansion to 6 patients was planned if dose limiting toxicity (DLT) occurred in the first cycle of treatment, and MTD was defined as the dose at which ≥ 2/6 patients experienced DLT. Results: 21 evaluable patients (11 male, 10 female patients median age 58 range 29–76) were treated; 6 at 10mg per day, 12 at 0.25mg/kg/day and 3 at 0.3mg/kg/day. Cycle 1 DLTs included fatigue (grade(G) 3 DLT in 1 patient at 10mg), G3 foot rash, proteinuria and hypertension in 1 patient each at 0.25mg/kg/day (RPTD) and 2 patients with G3 hypertension, including G3 proteinuria in one of these patients, at 0.3mg/kg/day (MTD). Other common treatment-related adverse events at RPTD included asthenia, myalgia, mouth irritation, pneumothorax related to cavitating lung nodule in 2 patients. Pharmacokinetics of ABT869 demonstrated oral clearance of 2.8 ± 1.2 L/h, (mean ± SD, N=16) and half-life of 16.9 ± 5.0 h, with minimal drug accumulation at day 15. 2 PRs were seen in NSCLC patients and stable disease > 4 TPs was observed in 12 patients, with CT scan evidence of cavitation of pulmonary disease and reduced DCE-MRI derived parameters. Mean peak plasma VEGF levels were increased significantly from baseline (p=0.031). CEPs and CECs were reduced in most patients by day 15. Conclusions: 0.25mg/kg/day is the RPTD of ABT869. Modulation of plasma VEGF, CECs and DCE MRI show drug activity consistent with antiangiogenic activity. Promising clinical activity is seen, particularly in NSCLC.

No significant financial relationships to disclose.

Dynamic contrast enhanced MRI (DCE MRI) for assessment of effects of anti-angiogenic therapy: Comparison of the transfer constant (Ktrans) to blood flow and permeability derived by a distributed parameters model

14109

Background: Transfer constant (Ktrans) and IAUC60 normalized with arterial input function are commonly used dynamic contrast enhanced magnetic resonance imaging (DCE MRI) parameters. The distributed parameters model (DP) is a DCE MRI model that enables derivation of blood flow and capillary permeability-surface area product (PS). We aim to study the distributed parameters model as an alternative method of angiogenesis assessment and correlate the above parameters to drug exposure and patient outcome in a Phase I anti- angiogenic trial. Methods: Fifteen evaluable patients from an on-going Phase I trial (ABT 869) with 3 dose escalations formed the study population. Pharmacokinetic study was performed on Day 1 and the area under the concentration time curve extrapolated to infinity (AUCinfinity) was used as an indicator of drug exposure. All patients underwent DCE MRI at baseline, Day 3 and Day 15 with temporal resolution of 4 seconds. Gadolinium concentrations were estimated using a dual flip angle method. Patients demonstrating progressive disease in first 2 evaluation scans (cycle 2 or 4) based on RECIST criteria were considered progressors and all other patients non-progressors. Receiver operating curve (ROC) analysis was performed. Correlation with AUCinfinity was analyzed. Results: There is good correlation (Spearman’s coefficient -0.67, p = 0.008) between AUCinfinity and DP derived PS and less strong correlation with normalized IAUC60 (Spearman’s coefficient -0.57, p = 0.03). There is no correlation for Ktrans (Spearman’s coefficient 0.04). ROC analysis for predicting progressors versus non-progressors showed a higher ROC area for PS compared to Ktrans (0.83 versus 0.47, p = 0.037). Normalized IAUC60 showed a slightly lower area compared to PS (0.77 versus 0.83) but the difference is not significant (p = 0.58). Conclusions: PS derived from DP model shows better correlation with drug exposure and may predict patient outcome better than Ktrans.

[Table: see text]

A phase II study of ABT-510 for the treatment of metastatic melanoma

8041

Background: ABT-510 is a synthetic peptide analog of thrombospondin-1 demonstrating inhibition of VEGF/bFGF mediated human endothelial cell migration, proliferation, tube formation, cornea-neovascularization as well as inhibition of tumor growth in vivo (B16F10 melanoma). Having been found to be safe in phase I testing, ABT-510 has entered phase II trials. Presented are the results of a phase II study using ABT-510 for the treatment of stage IV melanoma. Methods: A two stage phase II clinical trial was conducted to assess the anti-tumor activity, safety profile and pharmacodynamics of ABT510 in patients with stage IV melanoma. Patients self-administered 100mg of ABT-510 subcutaneously twice/day. Therapy was continued in the absence of excessive toxicity or tumor progression. Primary endpoint was 18 week progression free survival rate. Enrolled were patients at least 18 years of age with measurable (RECIST) metastatic melanoma, ECOG performance status of 0–2 and normal pre-registration blood tests. Exclusion criteria included: cancer therapy less than 4 weeks prior to registration; failure to recover from prior therapy; brain metastases; significant recent bleeding; uncontrolled hypertension; and ongoing anti-coagulation. Pregnant or nursing women were not eligible. Results: Twenty-one patients (67% male) were enrolled with a median age of 55 years. Most patients had M1c disease (80%) and 62% had prior chemotherapy for stage IV melanoma. None of the patients were ineligible/canceled participation. After the first stage of the trial was complete, only 3 of the first 20 patients enrolled were progression-free at 18 weeks. Having not met the minimal clinical efficacy requirement (at least 7 of the first 20 patients progression-free at 18 weeks) the trial was closed to further accrual. Correlative laboratory studies suggested decreases in some of the measured parameters of angiogenesis (VEGFC, circulating endothelial cells) with no impact on immune homeostasis. Conclusions: Single agent ABT-510 therapy administered at 100mg twice/day to patients with previously treated metastatic melanoma did not demonstrate significant clinical efficacy. However, changes in measured parameters of angiogenesis suggest possible clinical efficacy with higher dosing or in combination with cytotoxic therapy.

[Table: see text]

Phase I study of the thrombospondin-1-mimetic angiogenesis inhibitor ABT-510 with 5-fluorouracil and leucovorin: a safe combination

We performed a phase I study with the thrombospondin-1-mimetic angiogenesis inhibitor ABT-510 combined with 5-fluorouracil and leucovorin (5-FU/LV) to determine safety profile and assess pharmacokinetic interactions. Patients with advanced solid malignancies received LV 20 mg/m(2) followed by 5-FU 425 mg/m(2) both administered intravenously in 15 min daily for 5 days every 4 weeks. ABT-510 was administered subcutaneously twice daily continuously from day 2 onwards. Blood and urine samples for pharmacokinetic analyses were collected at days 1, 5 and 22. Twelve patients received a total of 45 cycles of 5-FU/LV combined with ABT-510. ABT-510 dose levels studied were 50 and 100 mg. The combination was well tolerated, with a toxicity profile comparable to that of 5-FU/LV alone. At the dose levels studied no significant pharmacokinetic interactions were observed. These data indicate that ABT-510 administered twice daily subcutaneously can be safely combined with 5-FU/LV administered daily for 5 days, every 4 weeks.

Phase II studies of bryostatin-1 in patients with advanced sarcoma and advanced head and neck cancer

BACKGROUND

Bryostatin 1 is a marine derived macrolactone with antineoplastic activity modulated through protein kinase C, and with good activity in in vitro and in vivo models. There are few drugs that offer palliation for metastatic soft-tissue sarcoma and head and neck cancer, and drugs with new mechanisms of action warrant detailed disease specific study.

PATIENTS AND METHODS

Two phase II studies for patients with incurable soft tissue sarcoma (12), or head and neck cancer (12) were conducted. Patients were treated with bryostatin, 120 mg/m2/72 hours every 2 weeks for 3 cycles prior to re-evaluation. Most patients had received prior chemotherapy.

RESULTS

No patients had objective responses to therapy. Six patients had brief periods of disease stabilization. Toxicity was generally mild, with myalgia being prominent (n=8). Hyponatremia, not previously described, occurred in 5 patients. The mechanism of this toxicity was unclear.

CONCLUSIONS

Bryosytatin 1 given as a single agent for advanced adult soft tissue sarcoma and head and neck cancer is inactive. Myalgia and hyponatremia were the predominant toxicities.

Concomitant chemoradiotherapy as primary therapy for locoregionally advanced head and neck cancer

PURPOSE

To achieve locoregional control of head and neck cancer, survival, and organ preservation using intensive concomitant chemoradiotherapy.

PATIENTS AND METHODS

This study was a phase II trial of chemoradiotherapy with cisplatin 100 mg/m(2) every 28 days, infusional fluorouracil 800 mg/m(2)/d for 5 days, hydroxyurea 1 g orally every 12 hours for 11 doses, and radiotherapy twice daily at 1.5 Gy/fraction on days 1 through 5 (total dose, 15 Gy). Five days of treatment were followed by 9 days of rest, during which time patients received granulocyte colony-stimulating factor. Five cycles (three with cisplatin) were administered over 10 weeks (total radiotherapy dose, </= 75 Gy). Adjuvant chemoprevention with retinoic acid and interferon alfa-2A was offered.

RESULTS

Seventy-six patients were treated (stage IV, 93%; N2, 54%; N3, 21%). At a median follow-up of 38 months, the 3-year progression-free survival is 72%, locoregional control 92%, systemic control 83%, and overall survival 55%. Toxicities included mucositis (grade 3, 45%; grade 4, 12%), neutropenia (grade 4, 39%), and thrombocytopenia (grade 4, 53%). Surgery at the primary site was performed in 13 patients, and 39 had neck dissection. A majority of patients declined adjuvant chemoprevention. Pharmacokinetic parameters were not prognostic of tumor control. Quality of life declined during treatment but returned from good to excellent by 12 months after treatment.

CONCLUSION

Intensive concomitant chemoradiotherapy leads to high locoregional control and survival rates with organ preservation and a reversal of the historical pattern of failure (distant > locoregional). Surgery after concomitant chemoradiotherapy is feasible. Compliance with adjuvant chemoprevention is poor. Identification of less toxic regimens and improved distant disease control emerge as important future research goals.

Characterization of CPT-11 hydrolysis by human liver carboxylesterase isoforms hCE-1 and hCE-2

7-Ethyl-10-[4-(1-piperidino)-1-piperidino] carbonyloxy-camptothecin (irinotecan; CPT-11) is a prodrug activated by carboxylesterase enzymes. We characterized the hydrolysis of CPT-11 by two recently identified human carboxylesterase (hCE) enzymes, hCE-1 and hCE-2. Km and Vmax for hCE-1 and hCE-2 are 43 microM and 0.53 nmol/min/mg protein and 3.4 microM and 2.5 nmol/min/mg protein, respectively. hCE-2 has a 12.5-fold higher affinity for CPT-11 and a 5-fold higher maximal rate of CPT-11 hydrolysis when compared with hCE-1. In cytotoxicity assays, incubation of 1 microM CPT-11 with hCE-2 (3.6 microg/ml) resulted in a 60% reduction in survival of SQ20b cells. No significant reduction in cell survival was observed after incubation of CPT-11 with hCE-1. These data indicate that hCE-2 is a high-affinity, high-velocity enzyme with respect to CPT-11. hCE-2 likely plays a substantial role in CPT-11 activation in human liver at relevant pharmacological concentrations.

Oral 5-FU alternatives for the treatment of head and neck cancer

The common clinical presentations of head and neck cancer include early (stage I or II) disease, locally or regionally advanced (stage III or IV, M0) disease, and recurrent or metastatic disease (< 5% of patients). Patients with stage I-II disease are usually cured following surgery or radiotherapy; those with more advanced disease, however, will benefit from chemotherapy--either as induction treatment to avoid surgery and preserve the larynx, or as simultaneous chemoradiotherapy for patients with locoregionally advanced disease; patients presenting with metastatic disease and those with recurrent disease receive chemotherapy as the primary treatment modality. The clinical experience with oral chemotherapy in head and neck cancer patients is limited, partly because of the anatomic location of the disease and complications of local treatment. At the University of Chicago, several regimens that include oral chemotherapy have been studied, including infusional 5-fluorouracil/oral hydroxyurea/radiotherapy, and eniluracil/oral 5-FU/radiotherapy. These trials and others assessing oral agents in the treatment of patients with head and neck cancer will be discussed.

Phase II trial of uracil/tegafur (UFT) plus leucovorin in patients with advanced pancreatic carcinoma: a University of Chicago phase II consortium study

BACKGROUND/OBJECTIVES

Uracil and tegafur in a 4:1 molar concentration ratio (UFT; Bristol-Myers Squibb, Wallingford, CT) has broad anti-tumor activity for cancers arising from the gastrointestinal tract. However, there are no published data regarding the efficacy of leucovorin-modulated UFT in patients with pancreatic cancer. The objective of this trial was to determine the activity and evaluate the toxicity of UFT plus oral calcium leucovorin in patients with advanced pancreatic adenocarcinoma.

PATIENTS AND METHODS

Fourteen patients with advanced measurable adenocarcinoma of the pancreas were enrolled onto the trial. Patients received 300 mg/m2/d UFT plus 90 mg/d leucovorin administered orally in divided doses every eight hours for 28 days repeated every 35 days. Objective tumor response was evaluated after two courses of therapy.

RESULTS

Fourteen patients were evaluable for response and toxicity. No objective responses were seen. The median (range) time to progression and survival were 14 (1.6-37), and 15 (1.9-62) weeks, respectively. Toxicity was mild with severe (grade 3 or 4) hyperbilirubinemia, pain, diarrhea, transaminitis, venous thrombus, weakness, renal failure, confusion, and edema/ascites seen in three (21%), one (7%), two (14%), one (7%), one (7%), one (7%), one (7%), one (7%), and two (14%) patients, respectively.

CONCLUSION

In the 14 patients evaluable, UFT 300 mg/m2/d plus oral leucovorin 90 mg/d administered for 28 days did not demonstrate anti-tumor activity against advanced pancreatic adenocarcinoma; however, this oral regimen was well tolerated and devoid of neutropenia, significant oral mucositis or diarrhea.