Abhimanyu Paraskar

Fullerenol-cytotoxic conjugates for cancer chemotherapy.

In the present study, we report the novel application of polyhydroxylated fullerenes (fullerenols) in cancer drug delivery. The facile synthetic procedure for generating multiple hydroxyl groups on the fullerene cage offers scope for high drug loading in addition to conferring hydrophilicity. Doxorubicin, a first line cancer chemotherapeutic, was conjugated to fullerenols through a carbamate linker, achieving ultrahigh loading efficiency. The drug-fullerenol conjugate was found to be relatively stable in phosphate buffer saline but temporally released the active drug when incubated with tumor cell lysate. The fullerenol-doxorubicin conjugate suppressed the proliferation of cancer cell-lines in vitro through a G2-M cell cycle block, resulting in apoptosis. Furthermore, in an in vivo murine tumor model, fullerenol-doxorubicin exhibited comparable antitumor efficacy as free drug without the systemic toxicity of free doxorubicin. Additionally, we demonstrate that the fullerenol platform can be extended to other chemotherapeutic agents, such as the slightly water-soluble cisplatin, and can emerge as a new paradigm in the management of cancer.

Cholesterol-tethered platinum II-based supramolecular nanoparticle increases antitumor efficacy and reduces nephrotoxicity

Nanoscale drug delivery vehicles have been harnessed extensively as carriers for cancer chemotherapeutics. However, traditional pharmaceutical approaches for nanoformulation have been a challenge with molecules that exhibit incompatible physicochemical properties, such as platinum-based chemotherapeutics. Here we propose a paradigm based on rational design of active molecules that facilitate supramolecular assembly in the nanoscale dimension. Using cisplatin as a template, we describe the synthesis of a unique platinum (II) tethered to a cholesterol backbone via a unique monocarboxylato and O→Pt coordination environment that facilitates nanoparticle assembly with a fixed ratio of phosphatidylcholine and 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-[amino (polyethylene glycol)-2000]. The nanoparticles formed exhibit lower IC50 values compared with carboplatin or cisplatin in vitro, and are active in cisplatin-resistant conditions. Additionally, the nanoparticles exhibit significantly enhanced in vivo antitumor efficacy in murine 4T1 breast cancer and in K-RasLSL/+/Ptenfl/fl ovarian cancer models with decreased systemic- and nephro-toxicity. Our results indicate that integrating rational drug design and supramolecular nanochemistry can emerge as a powerful strategy for drug development. Furthermore, given that platinum-based chemotherapeutics form the frontline therapy for a broad range of cancers, the increased efficacy and toxicity profile indicate the constructed nanostructure could translate into a next-generation platinum-based agent in the clinics.

Harnessing structure-activity relationship to engineer a cisplatin nanoparticle for enhanced antitumor efficacy

Cisplatin is a first line chemotherapy for most types of cancer. However, its use is dose-limited due to severe nephrotoxicity. Here we report the rational engineering of a novel nanoplatinate inspired by the mechanisms underlying cisplatin bioactivation. We engineered a novel polymer, glucosamine-functionalized polyisobutylene-maleic acid, where platinum (Pt) can be complexed to the monomeric units using a monocarboxylato and an O → Pt coordinate bond. We show that at a unique platinum to polymer ratio, this complex self-assembles into a nanoparticle, which releases cisplatin in a pH-dependent manner. The nanoparticles are rapidly internalized into the endolysosomal compartment of cancer cells, and exhibit an IC50 (4.25 ± 0.16 μM) comparable to that of free cisplatin (3.87 ± 0.37 μM), and superior to carboplatin (14.75 ± 0.38 μM). The nanoparticles exhibited significantly improved antitumor efficacy in terms of tumor growth delay in breast and lung cancers and tumor regression in a K-rasLSL/+/Ptenfl/fl ovarian cancer model. Furthermore, the nanoparticle treatment resulted in reduced systemic and nephrotoxicity, validated by decreased biodistribution of platinum to the kidney as quantified using inductively coupled plasma spectroscopy. Given the universal need for a better platinate, we anticipate this coupling of nanotechnology and structure-activity relationship to rationally reengineer cisplatin could have a major impact globally in the clinical treatment of cancer.

Coupling growth-factor engineering with nanotechnology for therapeutic angiogenesis

Therapeutic angiogenesis is an emerging paradigm for the management of ischemic pathologies. Proangiogenic Therapy is limited, however, by the current inability to deliver angiogenic factors in a sustained manner at the site of pathology. In this study, we investigated a unique nonglycosylated active fragment of hepatocyte growth factor/scatter factor, 1K1, which acts as a potent angiogenic agent in vitro and in a zebrafish embryo and a murine matrigel implant model. Furthermore, we demonstrate that nanoformulating 1K1 for sustained release temporally alters downstream signaling through the mitogen activated protein kinase pathway, and amplifies the angiogenic outcome. Merging protein engineering and nanotechnology offers exciting possibilities for the treatment of ischemic disease, and furthermore allows the selective targeting of downstream signaling pathways, which translates into discrete phenotypes.

Rationally engineered polymeric cisplatin nanoparticles for improved antitumor efficacy.

The use of cisplatin, a first line chemotherapy for most cancers, is dose-limited due to nephrotoxicity. While this toxicity can be addressed through nanotechnology, previous attempts at engineering cisplatin nanoparticles have been limited by the impact on the potency of cisplatin. Here we report the rational engineering of a novel cisplatin nanoparticle by harnessing a novel polyethylene glycol-functionalized poly-isobutylene-maleic acid (PEG-PIMA) copolymer, which can complex with cis-platinum (II) through a monocarboxylato and a coordinate bond. We show that this complex self-assembles into a nanoparticle, and exhibits an IC(50) = 0.77 ± 0.11 µM comparable to that of free cisplatin (IC(50) = 0.44 ± 0.09 µM). The nanoparticles are internalized into the endolysosomal compartment of cancer cells, and release cisplatin in a pH-dependent manner. Furthermore, the nanoparticles exhibit significantly improved antitumor efficacy in a 4T1 breast cancer model in vivo, with limited nephrotoxicity, which can be explained by preferential biodistribution in the tumor with reduced kidney concentrations. Our results suggest that the PEG-PIMA-cisplatin nanoparticle can emerge as an attractive solution to the challenges in cisplatin chemotherapy.

Rationally designed oxaliplatin-nanoparticle for enhanced antitumor efficacy

Nanoscale drug delivery vehicles have been extensively studied as carriers for cancer chemotherapeutics. However, the formulation of platinum chemotherapeutics in nanoparticles has been a challenge arising from their physicochemical properties. There are only a few reports describing oxaliplatin nanoparticles. In this study, we derivatized the monomeric units of a polyisobutylene maleic acid copolymer with glucosamine, which chelates trans-1,2-diaminocyclohexane (DACH) platinum (II) through a novel monocarboxylato and O --> Pt coordination linkage. At a specific polymer to platinum ratio, the complex self-assembled into a nanoparticle, where the polymeric units act as the leaving group, releasing DACH-platinum in a sustained pH-dependent manner. Sizing was done using dynamic light scatter and electron microscopy. The nanoparticles were evaluated for efficacy in vitro and in vivo. Biodistribution was quantified using inductively coupled plasma atomic absorption spectroscopy (ICP-AAS). The PIMA-GA-DACH-platinum nanoparticle was found to be more active than free oxaliplatin in vitro. In vivo, the nanoparticles resulted in greater tumor inhibition than oxaliplatin (equivalent to 5 mg kg⁻¹ platinum dose) with minimal nephrotoxicity or body weight loss. ICP-AAS revealed significant preferential tumor accumulation of platinum with reduced biodistribution to the kidney or liver following PIMA-GA-DACH-platinum nanoparticle administration as compared with free oxaliplatin. These results indicate that the rational engineering of a novel polymeric nanoparticle inspired by the bioactivation of oxaliplatin results in increased antitumor potency with reduced systemic toxicity compared with the parent cytotoxic. Rational design can emerge as an exciting strategy in the synthesis of nanomedicines for cancer chemotherapy.

Abstract 5488: Merging structure-activity relationship and nanotechnology to re-engineer cisplatin

The use of nanovectors holds the potential to revolutionize cancer chemotherapy by specifically targeting tumor. A number of polymeric nanovectors are currently in development or in clinics, and are dramatically altering the pharmacodynamics and pharmacokinetics profile of the active agent. However, most of these polymeric constructs decrease the potency of the conjugated active agent, relying on increased uptake into the tumor for the improved therapeutic index. Furthermore, the nanovector formulation of small molecules such as cisplatin, which is a first-line therapy for multiple cancers, has been a challenge. So there is an urgent need to design a nanoparticle which will release a drug at its target site without decreasing efficacy of cisplatin. In the present study, we synthesized cisplatin-poly-isobutylene-maleic acid modified with glucosamine conjugate, which self assembles into nanoparticles with unique size depending on cisplatin to polymer ratio. The poly-isobutylene-maleic acid modification with glucosamine, mimicking glycans, not only increases hydrophilicity but also gives unique structural facilitation to polymer backbone so it can hold cisplatin by caboxylato and coordinate bond. The release kinetics of these nanoparticles reveals that the cisplatin release is pH dependent, and is released faster in lower pH than neutral or basic condition. We found that the these nanoparticles were taken up by cancer cells within 6 hours and inhibited proliferation and induced apoptosis in lung and breast cancer cells in vitro. In an in vivo lung and breast cancer models, the nanoparticles reduce tumor growth significantly with reduced systemic toxicity as compared to free cisplatin. In conclusion we have demonstrated that rationally re-engineered cisplatin nanoparticles improved therapeutic index for lung, breast and transgenic ovarian murine cancer models, which can be harnessed in the clinical management of cancer. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 5488.

Abstract 3520: Pegylated nanoplatinates: A novel re-engineered cisplatin for cancer chemotherapy

Proceedings: AACR 101st Annual Meeting 2010‐‐ Apr 17‐21, 2010; Washington, DC Cis-diamminedichloroplatinum (II) (CDDP) is a platinum based chemotherapy drug used to treat various types of cancers, including sarcomas, some carcinomas, lymphomas, and germ cell tumors. There are two major concerns of cisplatin based chemotherapy: first is relapse of cancer in majority of pateints with cisplatin resistant disease and second is cisplatin associated nephrotoxicity (kidney damage). In the present study, we have demonstrated that cisplatin can be complexed using a carboxylato bond with poly-isobutylene-maleic acid, derivatized with a polyethylene glycol moiety. We found that at unique cisplatin to polymer ratio, this conjugate self-assembles into nanoparticles, and exhibits enhanced therapeutic efficacy without any nephrotoxicity as compared with cisplatin in murine lewis lung carcinoma model. The PIMA-PEG-CDDP conjugate inhibited proliferation and induced apoptosis in Lewis lung carcinoma and 4T1 breast cancer cells in vitro. The nanoparticles were taken up by cancer cells through endocytosis within 6 hours and retained in subcellular compartment over 24 hours in 4T1 breast cancer cells. Furthermore, in an in vivo 4T1 breast cancer model, PIMA-PEG-CDDP nanoparticles reduce tumor growth drastically with no side effects, thus increasing the survival rate of the mice as compared to free cisplatin treated mice. Thus our studies showed that pegylated-PIMA-CDDP can be harnessed for lung and breast cancer chemotherapy with increased therapeutic index compared with cisplatin. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 3520.