✓ Sustained drug delivery by biodegradable polymer devices can increase the therapeutic efficacy of drugs by producing high local tissue concentrations over extended periods of time. It has been shown previously that implantation of controlled-release polymers impregnated with the nitrosourea carmustine (BCNU) extended the period of survival in rats bearing the 9L glioma compared with similar rats treated with systemically administered BCNU. This study evaluated the effect on the monkey brain of interstitial delivery of BCNU by the biodegradable polyanhydride copolymer poly[bis(p-carboxyphenoxy)propane]anhydride (PCPP) and sebacic acid (SA) in a 20:80 formulation (PCPP:SA). The effect of combining interstitial BCNU with radiation therapy was also evaluated. Eighteen male cynomologus monkeys were randomly assigned to one of four groups: a control group; a group with implantation of empty polymer; a group with implantation of BCNU-loaded polymer; and a group with implantation of empty polymer in the right hemisphere and BCNU-loaded polymer in the left hemisphere, followed by irradiation. The effects were evaluated radiologically and histologically at specified times. A local reaction by the brain to the polymer was found, which was greater when the polymer contained BCNU. Local cerebral edema was observed radiographically on postoperative Day 14 and had resolved by Day 72. Histologically, a subacute cellular inflammatory response was seen on postoperative Day 16, which had changed to a chronic inflammatory response by Day 72. In the group with radiation therapy administered to the hemisphere bearing BCNU-loaded polymer, only localized pathological changes were detected. In all animals, brain distant from the polymer implantation site was normal. No neurological or general deleterious effects were seen in any of the animals. It is concluded that the interstitial delivery of BCNU by the polyanhydride polymer PCPP:SA is safe in the primate brain and that concomitant radiation therapy did not lead to any adverse effects. These experimental findings are important to an understanding of the clinical effects of PCPP:SA implants in treating brain diseases.
Henry Brem, Rafael J. Tamargo, Alessandro Olivi, Michael Pinn, Jon D. Weingart, Moody Wharam, and Jonathan I. Epstein
Kevin D. Judy, Alessandro Olivi, Kwame G. Buahin, Abraham Domb, Jonathan I. Epstein, O. Michael Colvin, and Henry Brem
✓ Most malignant gliomas grow despite treatment by standard chemotherapeutic agents. The authors explored the use of an innovative drug, 4-hydroperoxycyclophosphamide (4HC), delivered via a controlled-release biodegradable polymer to determine whether local delivery would enhance efficacy. This drug is an alkylator-type chemotherapeutic agent derived from cyclophosphamide. Unlike the parent drug, which requires activation by hepatic microsomes, 4HC is active in vitro. Two rat glioma cell lines, 9L and F98, were treated in cell culture with medium containing 4HC. Both cell lines were more sensitive to 4HC than to a nitrosourea, BCNU, an agent of established value in the local therapy of gliomas.
Ninety Fischer 344 rats implanted with 9L or F98 gliomas were treated with an intracranial polymer implant containing 0% to 50% loaded 4HC in the polymer, and it was found that 20% 4HC—loaded polymers caused minimum local brain toxicity and maximum survival. These polymers were then used to compare the in vivo efficacy of 4HC to BCNU in rats implanted with 9L glioma. Animals with brain tumors treated with 4HC had a median survival span of 77 days compared to the median survival of 21 days in BCNU-treated animals and median survival of 14 days in untreated animals. Long-term survival for more than 80 days was 40% in the 4HC-treated rats versus 30% in the BCNU-treated rats.
The polymer carrier used in this study was a copolyanhydride of dimer erucic acid and sebacic acid 1:1, which was able to maintain the hydrolytically unstable 4HC in a stable state for local delivery. Thus, it is concluded that 4HC-impregnated polymers provide an effective and safe local treatment for rat glioma.