Sunitinib is an ATP competitive tyrosine kinase inhibitor of several membrane receptors including VEGFR-1, -2, and -3, PDGFR-α and -β, c-KIT, CSF-1R, FLT-3, and RET. Through this molecular mode of action, sunitinib is able to avoid tumoral angiogenesis and proliferation. Sunitinib is already approved by the FDA, EMEA and AEMPS for the treatment of patients with metastatic renal cell carcinomas and those with metastatic gastrointestinal stromal tumors (GIST) with progression or intolerance to imatinib.

Suntinib has recently reported to be superior than placebo in terms of response rate (9.3% vs. 0%; p<0.05), progression free survival (11.4 vs. 5,5 months; HR 0.41;p<0.05), and overall survival (HR 0.40;p<0.05) when administered in a phase 3 trial to patients with advanced pancreatic neuroendocrine tumors (NETs).

Sunitinib is an expensive drug that drains the budget of health public system therefore it demands a rational drug use.

Sunitinib is metabolized by CYP3A4, that belongs to the P450 cytochrome system in the liver. Most of the drug is eliminated in faeces and only 16% by urine. Sunitinib has no food-effect when taken with meals. Pharmacokinetics parameters did not differ between cancer patients and healthy volunteers.

Houk et al. Showed that the area under the curve of plasmatic concentration of sunitinib and its active metabolite did correlate with clinical outcome. In other words, the higher plasma concentration area under the curve the highest rates of radiological response, progression free and overall survival rates.

Ketoconazol is an antifungal drug that inhibits the CY3A4 inducing an elevation of peak plasma levels of other drugs administered simultaneously and that are metabolized by the same system. In the labeling sheet of sunitinib it is said that ketoconazol induced a 49% and 51% of increase of plasmatic sunitinib Cmax y AUC0-∞ when both drugs were administered together. This fact makes that the investigatorspropose that by administering both drugs simultaneously the investigators could reduce sunitinib dose by a lower metabolization with similar plasma concentration. The dose reduction would impact in drug cost.

Here the investigators propose to determine the most optimal combination dose of sunitinib (25 mg or 37.5 mg) and ketoconazol (200mg o 400mg) by which the investigators could have plasmatic bioequivalent concentrations compared with single dose of sunitinib 50mg.

Each volunteer will be assigned to a treatment arm (Arm A and Arm B). Volunteers included in Arm A will take: sunitinib 50 mg, sunitinib 37.5 mg + ketoconazole 200 mg and sunitinib 37.5 mg + 400 mg ketoconazole. Volunteers included in Arm B will take: sunitinib 50 mg, sunitinib 25 mg + ketoconazole 200 mg and sunitinib 25 mg + 400 mg ketoconazole

This is a phase I, pilot, open, randomized, parallel, and cross-over trial to assess the interaction between three different dose levels of sunitinib (50 mg, 37.5 mg, and 25 mg) and two dose levels of ketoconazole (200 mg and 400 mg) in 12 healthy volunteers (6 voluunteers in each group of treatment) Each volunteer will be assigned to a treatment arm (Arm A and Arm B. Volunteers included in Arm A will take: sunitinib 50 mg, sunitinib 37.5 mg + ketoconazole 200 mg and sunitinib 37.5 mg + 400 mg ketoconazole. Volunteers included in Arm B will take: sunitinib 50 mg, sunitinib 25 mg + ketoconazole 200 mg and sunitinib 25 mg + 400 mg ketoconazole

Inclusion Criteria:

• Healthy individuals men who give their written consent to participate in the study, after having received information about the design, the project objectives, the risks and that at any moment they can refuse their cooperation.
• Age between 18 and 35 years.
• Subjects with a BMI that is between 19 and 28.
• Healthy subjects, without any organic or psychological pathology.
• Clinical history and physical examination within normal limits.
• Lack of clinically relevant abnormalities in blood test (hematology, biochemistry, virology) and urine test
• Vital signs and electrocardiographic recording in the normal range.

Exclusion Criteria:

• Subjects suffering from organic or psychological pathology. Prior to the inclusion of any volunteer it should be considered all security parameters mentioned in the protocol (biochemical markers of kidney damage and / or liver out of the normal range set by the laboratory).
• Subjects who have received prescription drug treatment in the last 15 days or any medication within 48 hours before receiving study medication.
• Known hypersensitivity to any drug
• Suspected of drug abuse