ABSTRACT
Von Hippel-Lindau (VHL) disease is an autosomal dominant disease occurring in 1 in 35,000 births and leads to an increased risk of a phenotypically diverse array of tumor types including, but not limited to, clear cell renal cell carcinoma (ccRCC) and hemangioblastomas (HBs). Previous studies of patients with VHL disease treated with the tyrosine kinase inhibitor (TKI) sunitinib did not show clinical response in HBs. Interestingly, VHL-related HBs displayed increased fibroblast growth factor receptor 3 (FGFR3) protein expression when compared to VHL-related ccRCCs. Therefore, in this pilot study, we assessed the safety and efficacy profile of TKI 258 (dovitinib), a multi-tyrosine kinase inhibitor of VEGF receptor and fibroblast growth factor (FGF), in patients with VHL disease who had measureable HBs. The trial was stopped after six patients enrolled after the toxicity stopping rule was triggered. With regards to safety, 6/6 subjects had at least one adverse event (AE). Best response in 6/6 subjects was stable disease (SD) in HBs. While the negative safety and efficacy results of this pilot study do not favor the use of dovitinib for the treatment of asymptomatic HBs in VHL disease patients, further investigation into alternative scheduling and other FGFR inhibitors for the treatment of HBs in VHL disease patients is warranted given the promising pre-clinical and molecular data.
ABSTRACT
BACKGROUND: Receptors in tumor blood vessels are attractive targets for ligand-directed drug discovery and development. The authors have worked systematically to map human endothelial receptors ("vascular zip codes") within tumors through direct peptide library selection in cancer patients. Previously, they selected a ligand-binding motif to the interleukin-11 receptor alpha (IL-11Rα) in the human vasculature. METHODS: The authors generated a ligand-directed, peptidomimetic drug (bone metastasis-targeting peptidomimetic-11 [BMTP-11]) for IL-11Rα-based human tumor vascular targeting. Preclinical studies (efficacy/toxicity) included evaluating BMTP-11 in prostate cancer xenograft models, drug localization, targeted apoptotic effects, pharmacokinetic/pharmacodynamic analyses, and dose-range determination, including formal (good laboratory practice) toxicity across rodent and nonhuman primate species. The initial BMTP-11 clinical development also is reported based on a single-institution, open-label, first-in-class, first-in-man trial (National Clinical Trials number NCT00872157) in patients with metastatic, castrate-resistant prostate cancer. RESULTS: BMTP-11 was preclinically promising and, thus, was chosen for clinical development in patients. Limited numbers of patients who had castrate-resistant prostate cancer with osteoblastic bone metastases were enrolled into a phase 0 trial with biology-driven endpoints. The authors demonstrated biopsy-verified localization of BMTP-11 to tumors in the bone marrow and drug-induced apoptosis in all patients. Moreover, the maximum tolerated dose was identified on a weekly schedule (20-30 mg/m(2) ). Finally, a renal dose-limiting toxicity was determined, namely, dose-dependent, reversible nephrotoxicity with proteinuria and casts involving increased serum creatinine. CONCLUSIONS: These biologic endpoints establish BMTP-11 as a targeted drug candidate in metastatic, castrate-resistant prostate cancer. Within a larger discovery context, the current findings indicate that functional tumor vascular ligand-receptor targeting systems may be identified through direct combinatorial selection of peptide libraries in cancer patients.
