Use of Individual Pharmacokinetically (PK)-Guided Sunitinib Dosing: A Feasibility Study in Patients With Advanced Solid Tumors

Sunitinib is an orally available inhibitor of vascular endothelial growth factor (VEGFR), platelet-derived growth factor (PDGF), cytokine receptor (c-KIT), and receptor tyrosine kinase (FLT-3) activity. Sunitinib is proven effective as single agent in several solid tumor types and is approved for use in advanced renal cell cancer (RCC) and imatinib-resistant or -intolerant gastrointestinal stromal tumors (GISTs). However, in a large percentage of patients (30 and 50%), dose reductions are required because of multiple grade 2 toxicities or due to grade 3 or 4 toxicities. Therefore, the currently used dosing schedule is not optimal.

Recently, a dose-efficacy relation was established for sunitinib treatment. This large meta-analysis of pharmacokinetic/pharmacodynamic data from studies performed in mRCC patients, GIST patients and patients with solid tumors, clearly showed a relationship between sunitinib exposure and efficacy and tolerability. Both time to progression (TTP) and overall survival (OS) were significantly better for mRCC patients with high area under the curve (AUC) compared to low AUC. This was not only observed for sunitinib exposure but also for its active metabolite SU12662. In addition, there was a significant relationship between exposure and probability of partial response (PR) or complete response (CR) in mRCC patients (p=0.00001), indicating that a dose intensity in patients should be as high as possible. Target plasma concentrations of sunitinib plus metabolite (N-desethyl sunitinib) are in the range of 50 to 100 ng/mL, as deduced from pharmacokinetic (PK) / pharmacodynamic (PD) preclinical data. Since the dose-efficacy relation for sunitinib treatment is solely established in a retrospective (meta-) analysis from patients treated in several studies, we propose to perform a prospective feasibility study in 30 patients with PK guided dosing of sunitinib. If PK guided once-daily continuous sunitinib dosing is feasible, a RCT in mRCC patients will be performed comparing PK guided dosing with a standard sunitinib dosing schedule.

Inclusion criteria

• Histopathologically confirmed advanced tumors for which sunitinib is considered standard or patients with advanced or metastatic tumors for whom no standard therapy is available;
• Age more then 18 years;
• Able and willing to give written informed consent;
• Able and willing to undergo blood sampling for pharmacogenetic and pharmacokinetic analysis;
• Able and willing to undergo a tumor biopsy for DNA sequencing;
• Able to swallow oral medications
• Life expectancy more then 3 months, allowing adequate follow up of toxicity evaluation and antitumor activity;
• WHO performance status of 0 or 1;
• Evaluable disease according to RECIST 1.1 criteria;
• Minimal acceptable safety laboratory values

• ANC of => 1.5 x 109 /L
• Platelet count of => 100 x 109 /L
• Hepatic function as defined by serum bilirubin => 1.5 x ULN, ASAT and ALAT
• 2.5 x ULN
• Renal function as defined by serum creatinine => 1.5 x ULN or creatinine clearance => 50 mL/min (by Cockcroft-Gault formula);
• No radio- or chemotherapy or other investigational drug treatment within the last 4 weeks prior to study entry, with the exception of palliative radiotherapy (8 Gy or on the extremities).

Exclusion criteria

• Current treatment in another therapeutic clinical trial
• Congestive heart failure, myocardial infarction or coronary artery bypass graft in the previous six months, ongoing severe or unstable angina or any unstable arrhythmia requiring medication
• Patients with known alcoholism, drug addiction and/or psychotic disorders in the history that are not suitable for adequate follow up
• Women who are pregnant or breast feeding.
• Both men and women enrolled in this trial must agree to use a reliable contraceptive method throughout the study (definition of adequate contraceptive methods will be based on the judgment of the principal investigator or a designated associate).
• Legal incapacity
• Known allergy/intolerance to sunitinib or any of the excipients