Abstract 3221: Multifunctional nano-bioconjugate based on poly(β-L-malic acid) for temozolomide delivery for brain tumor treatment
Authors: Patil Rameshwar , Inoue Satoshi , Portilla-Arias José , Konda Bindu , Espinoza Andres , Ding Hui , Elramsisy Adam , Black Keith L. , Holler Eggehard , Ljubimova Julia Y. 
Published: June 2012

Temozolomide (TMZ) is a DNA alkylating agent that is the most effective drug to treat patients with glial tumors when combined with radiation. However, TMZ is toxic and therapeutic dosages are limited by severe side effects. We have successfully conjugated temozolomide and synthesized an efficient drug delivery system using a naturally derived, biodegradable, non-toxic and non-immunogenic platform: polymalic acid (PMLA). This new nanoconjugate drug delivery system is designed to improve treatment efficiency and reduce non-tumor tissue toxicity.

Methods: PMLA of microbial origin was obtained by cultivation of Physarum polycephalum. Temozolomide was converted to its hydrazide prior to conjugation to PMLA platform. Nanoconjugates were characterized with respect to their absolute molecular weight (Mw), size and zeta potential using a Malvern Zetasizer. Half-life of temozolomide was measured in PBS at 37°C. Degradation assays in PBS and human plasma were carried out at 37°C. For cell uptake study using U-87 MG cells, nanoconjugates were labeled with Alexa Fluor 680. For in vivo study, U-87 MG cells (1 million) were inoculated subcutaneously into nude mice. Drugs were administered I.V. for 5 consecutive days and tumor size was measured.

Results: The multi-component drug delivery system synthesized using PMLA as a platform consisted of varied amounts of prodrug TMZ in its hydrazide form, trileucine (LLL) for membrane disruption, antibodies for targeting, PEG for stability and Alexa Fluor 680 for imaging. Water soluble TMZ nanoconjugates showed hydrodynamic diameters ranging from 7 to 15 nm and zeta potentials from -6 to -18 mV. TMZ conjugated with polymer significantly improved its half-life from 1.8 h (for free TMZ) to 5-7 h. 50% degradation of nanoconjugate in human plasma was observed in 12-40 h at 37°C. The strongest reduction of human brain and breast cancer cell viability was obtained by versions of TMZ nanoconjugates containing LLL with or without anti-TfR antibody. TMZ-resistant cancer cell lines such as T98G, MDA-MB-231 and MDA-MB-468 were responsive to TMZ-nanoconjugate treatment. During in vivo study, TMZ-nanoconjugate (4 mg/kg of TMZ) produced a strong reduction of tumor size compared to PBS (p=0.0024, p=0.0018 for free temozolomide at same dose).

Conclusions: The new versatile, biocompatible and biodegradable TMZ-nanoconjugates effectively reduced cancer cell growth of human glioma U-87-MG cells and three TMZ resistant cancer cell lines. Further, nanoconjugates proved their efficacy on subcutaneous U-87 MG xenografts and significantly reduced the tumor volume compared to controls. Temozolomide conjugated with polymers could be a promising next generation therapy for targeted brain tumor treatment with reduced side effects in the near future.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 3221. doi:10.1158/1538-7445.AM2011-3221