Hydroxyurea + Imatinib + Vatalanib

The combination of hydroxyurea, imatinib, and vatalanib is a multi-targeted therapy that has been studied primarily for the treatment of malignant gliomas, particularly glioblastoma multiforme. This combination approach aims to simultaneously inhibit multiple pathways involved in tumor growth and angiogenesis. Hydroxyurea is a traditional chemotherapeutic agent, while imatinib mesylate (Gleevec) targets platelet-derived growth factor receptors (PDGFR). Vatalanib is an oral angiogenesis inhibitor that primarily targets vascular endothelial growth factor receptors (VEGFR)[1][5]. The rationale behind this combination is to target both tumor cells directly and their blood supply by inhibiting angiogenesis[2][8]. Clinical trials, including Phase I studies, have shown that this combination is generally well-tolerated with manageable side effects. The maximum tolerated dose (MTD) of vatalanib when combined with standard doses of imatinib and hydroxyurea was determined to be 1000 mg twice daily[1][4]. Common adverse effects included hematologic toxicities, gastrointestinal issues, fatigue, and hypertension[6]. In terms of efficacy, early clinical trials showed encouraging rates of radiographic response, with some patients achieving partial responses or stable disease[6][9]. However, the combination has not progressed to standard-of-care treatment for malignant gliomas. ## Dosing Information In clinical trials, the dosing regimen typically included: - Hydroxyurea: 500 mg twice daily - Imatinib: 400 mg daily for patients not taking enzyme-inducing antiepileptic drugs (EIAEDs) or 500 mg twice daily for patients taking EIAEDs - Vatalanib: Escalated from 500 mg to 1250 mg twice daily in successive cohorts, with the MTD established at 1000 mg twice daily[1][5] ## Mechanism of Action This combination therapy works through multiple mechanisms: - **Hydroxyurea**: Inhibits DNA synthesis by blocking ribonucleotide reductase - **Imatinib mesylate**: Inhibits platelet-derived growth factor receptors (PDGFR), targeting pericytes in tumor blood vessels - **Vatalanib**: Inhibits vascular endothelial growth factor receptors (VEGFR), targeting endothelial cells in tumor blood vessels[1][7] Together, these agents aim to disrupt both tumor cell growth and the formation of new blood vessels that supply the tumor with nutrients and oxygen[2][6].