Synthesis and Preclinical Evaluation of the First Carbon-11 Labeled PET Tracers Targeting Substance P1-7.

Two potent SP1-7 peptidomimetics have been successfully radiolabeled via [11C]CO2-fixation with excellent yields, purity, and molar activity. l-[11C]SP1-7-peptidomimetic exhibited promising ex vivo biodistribution profile. Metabolite analysis showed that l-[11C]SP1-7-peptidomimetic is stable in brain and spinal cord, whereas rapid metabolic degradation occurs in rat plasma. Metabolic stability can be significantly improved by substituting l-Phe for d-Phe, preserving 70% more of intact tracer and resulting in better brain and spinal cord tracer retention. Positron emission tomography (PET) scanning confirmed moderate brain (1.5 SUV; peak at 3 min) and spinal cord (1.0 SUV; peak at 10 min) uptake for l- and d-[11C]SP1-7-peptidomimetic. A slight decrease in SUV value was observed after pretreatment with natural peptide SP1-7 in spinal cord for l-[11C]SP1-7-peptidomimetic. On the contrary, blocking using cold analogues of l- and d-[11C]tracers did not reduce the tracers' brain and spinal cord exposure. In summary, PET scanning of l- and d-[11C]SP1-7-peptidomimetics confirms rapid blood-brain barrier and blood-spinal-cord barrier penetration. Therefore, further validation of these two tracers targeting SP1-7 is needed in order to define a new PET imaging target and select its most appropriate radiopharmaceutical.

Therapeutic targeting of membrane-associated GRP78 in leukemia and lymphoma: preclinical efficacy in vitro and formal toxicity study of BMTP-78 in rodents and primates.

Translation of drug candidates into clinical settings requires demonstration of preclinical efficacy and formal toxicology analysis for filling an Investigational New Drug (IND) application with the US Food and Drug Administration (FDA). Here, we investigate the membrane-associated glucose response protein 78 (GRP78) as a therapeutic target in leukemia and lymphoma. We evaluated the efficacy of the GRP78-targeted proapoptotic drug bone metastasis targeting peptidomimetic 78 (BMTP-78), a member of the D(KLAKLAK)2-containing class of agents. BMTP-78 was validated in cells from patients with acute myeloid leukemia and in a panel of human leukemia and lymphoma cell lines, where it induced dose-dependent cytotoxicity in all samples tested. Based on the in vitro efficacy of BMTP-78, we performed formal good laboratory practice toxicology studies in both rodents (mice and rats) and nonhuman primates (cynomolgus and rhesus monkeys). These analyses represent required steps towards an IND application of BMTP-78 for theranostic first-in-human clinical trials.

Gold(III)-dithiocarbamato peptidomimetics in the forefront of the targeted anticancer therapy: preclinical studies against human breast neoplasia.

Since the serendipitous discovery of cisplatin, platinum-based drugs have become well-established antitumor agents, despite the fact that their clinical use is limited by many severe side-effects. In order to both improve the chemotherapeutic index and broaden the therapeutic spectrum of current drugs, our most recent anti-neoplastic agents, Au(III) complexes, were designed as carrier-mediated delivery systems exploiting peptide transporters, which are up-regulated in some cancers. Among all, we focused on two compounds and tested them on human MDA-MB-231 (resistant to cisplatin) breast cancer cell cultures and xenografts, discovering the proteasome as a major target both in vitro and in vivo. 53% inhibition of breast tumor growth in mice was observed after 27 days of treatment at 1.0 mg kg(-1) d(-1), compared to control. Remarkably, if only the most responsive mice are taken into account, 85% growth inhibition, with some animals showing tumor shrinkage, was observed after 13 days. These results led us to file an international patent, recognizing this class of gold(III) peptidomimetics as suitable candidates for entering phase I clinical trials.

Physicochemical characteristics and in vitro release from oil-based vehicles of peptidomimetics: parenteral depots for intra-articular administration.

RESULTS: Basic physicochemical properties including their apparent solubility in aqueous buffer and vegetable oils of a series of 11 peptidomimetics varying with respect to chain length and degree of N-methylation were estimated. It was observed that the compounds in contact with water transformed into sticky, slowly dissolving semisolid materials. Based on these observations, the in vitro release behavior of selected peptide derivatives from oil solutions and in situ formed precipitates was investigated using a validated in vitro release model. CONCLUSION: The results of this investigation suggest that both types of oil-based drug delivery systems might constitute alternative sustained release formulation principles of such amorphous peptide derivatives for the intra-articular route of administration.