Exposure-Response (Safety) Analysis to Identify Linifanib Dose for a Phase III Study in Patients With Hepatocellular Carcinoma

Background

Hepatocellular carcinoma (HCC) is the third most common cause of cancer-related deaths and the fifth most common cancer globally. Hepatocellular carcinoma produces highly vascular tumors that overexpress vascular endothelial growth factor (VEGF), thus making VEGF a promising therapeutic target. The competitive inhibitor linifanib (ABT-869) has selectivity for VEGF and platelet-derived growth factor (PDGF) receptors and minimal activity against unrelated tyrosine and serine and threonine kinases. However, the optimal dosing regimen for linifanib in HCC patients is not yet known.

Objective

This study attempts to identify a linifanib dose or dosing regimen with an acceptable safety profile for a Phase III study in HCC patients.

Methods

The pharmacokinetic (PK) properties of linifanib were characterized from 2 Phase I and 3 Phase II clinical trials. Of the 266 patients evaluated, the median weight was 68 kg (range, 35-177 kg), 64% were male, and 87.6% of patients received an oral solution of linifanib, whereas 12.4% received a tablet formulation. Approximately 95% of patients received drug based on weight, with the remaining on a fixed-dosing regimen. A population PK analysis was conducted to characterize the linifanib exposure for each patient. Linifanib C_max and AUC derived from the population PK properties were correlated with the rates of adverse events (AEs).

Results

Linifanib PK properties are dose proportional for the 0.10-mg/kg to 0.25-mg/kg once daily dose range and are time independent after repeated oral dosing. The T_max of linifanib is approximately 3 hours, and the t_½ is approximately 1 day. The most common AEs related to linifanib PK were hypertension (P = 0.02 for C_max and P = 0.01 for AUC), diarrhea (P = 0.001 for C_max and P = 0.0012 for AUC), proteinuria (P = 0.001 for C_max and P = 0.002 for AUC), and asthenia (P = 0.03 for AUC). Weight and sex were identified as covariates for C_max, and sex was identified as a covariate for AUC. The predicted AE range for females was slightly higher compared with males; however, the AE range is tighter for the weight range for fixed dosing compared with weight-based dosing, regardless of sex.

Conclusions

The PK properties of linifanib support a one-compartment model with first-order absorption and elimination. Comparison of weight-based and fixed dosing revealed predicted AE rates to be similar, with a tighter AE range for fixed dosing. The safety profile of linifanib, therefore, supports a 17.5 mg fixed starting dose for Phase III clinical studies.