Hyaluronidase pretreatment produces selective melphalan enrichment in malignant melanoma implanted in nude mice

Preclinical and clinical observations suggest that the administration of hyaluronidase (Hyase) shortly before that of chemotherapy increases the access and, thus, the effectiveness of aniticancer drugs in tumors. To examine this hypothesis as well as the selectivity of such a therapeutic approach potentially beneficial in isolated limb perfusion, the Hyase-induced distribution of melphalan was measured in tumor-bearing nude mice with respect to the mode of drug administration using RP-18 ion-pair high-performance liquid chromatography (HPLC) with fluorimetric detection. Melphalan alone (50 μmol/kg) or a combination of melphalan (50 μmol/kg) and Hyase (100,000 IU/kg) was injected either i.p. or s.c. in the vicinity of the tumors. The s.c. melphalan injection caused a 4-fold rise in melphalan concentration (59 μM) in the tumors as compared with i.p. application (15 μM). Only minor effects were observed with respect to the route of melphalan application on its distribution in other tissues (ca. 13 μM in plasma, 15 μM in muscle, 30 μM in the liver, 26 μM in the kidney, and 21 μM in the testicle). Irrespective of the route of Hyase coadministration, the enzyme increased the concentration of i.p. injected melphalan in all tissues to ca. 20 μM in the tumor, 15 μM in plasma, 27 μM in muscle, 40 μM in the liver, 29 μM in the kidney, and 28 μM in the testicle. In contrast, s.c. injected melphalan was selectively accumulated by the tumors after both s.c. and i.p. Hyase administration (462 and 388 μM, respectively). Melphalan enrichment in the tumors was higher (16- to 32-fold higher than in the other tissues) after i.p. administration of Hyase since, in contrast to s.c. injection of the enzyme, its i.p. administration caused a decrease in the concentration of the cytostatic in all other tissues as compared with the s.c. administration of melphalan alone.