A polymeric drug delivery system for the simultaneous delivery of drugs activatable by enzymes and/or light

Abstract

Three water soluble copolymers based on N-(2-hydroxypropyl)methacrylamide were prepared. Copolymer I contains adriamycin, a chemotherapeutic agent, attached via enzymatically degradable oligopeptide (glycylphenylalanylleucylglycine; G-F-L-G) side chains. The other two copolymers contained the photosensitizer, meso-chlorin e6 monoethylene diamine disodium salt (Mce6). In Copolymer II, the chlorin is attached via the degradable G-F-L-G sequence, and it was bound by the nondegradable glycyl spacer in Copolymer III. Initially, the copolymers were characterized separately in vitro and in vivo. Combinations of the copolymer bound chemotherapeutic agent and each of the copolymer bound photosensitizers were then assessed for antitumor effect in vivo. Localization/retention studies (A/J mice; Neuro 2A neuroblastoma solid tumor) were performed with the two copolymers containing Mce6 as well as the free drug. Results of these experiments demonstrated a very different tumor uptake profile for the two copolymers. While the free drug was rapidly cleared from tumor tissue, the copolymer containing Mce6 attached via the non-degradable bond was retained for an extended period; drug concentrations in the tumor were high even after 5 days. On the other hand, a high concentration of the copolymer containing Mce6 bound via the degradable sequence was taken up by the tumor, yet its concentration in the tumor was substantially diminished at 48 h after administration. This shows indirect evidence of in vivo cleavage of Mce6 from the copolymer in the lysosomal compartment which is supported by direct evidence of cleavage by cathepsin B (a lysosomal enzyme) in vitro. Antitumor effects were assessed on Neuro 2A neuroblastoma induced in A/J mice for all three copolymers. Photodynamic therapy (PDT) proved the copolymer with Mce6 bound via the degradable oligopeptide sequence to be a more effective photosensitizer in vivo than the other chlorin containing copolymer. The difference in activity was consistent with the results obtained by photophysical analyses in which the free drug had a higher quantum yield of singlet oxygen generation than the polymer bound drug in buffer. The quantum yield of singlet oxygen generation increased with the enzymatic cleavage of the chlorin from the copolymer. Conditions were subsequently determined for which chemotherapy or PDT would show some antitumor effect, yet be incapable of curing tumors. Finally, combination therapy experiments were performed in which the copolymer bound adriamycin was mixed with either of the copolymer bound chlorin compounds and injected intravenously (i.v.) into the tail veins of mice.(ABSTRACT TRUNCATED AT 400 WORDS)

In vivo fluorescence imaging of the transport of charged chlorin e6 conjugates in a rat orthotopic prostate tumour

“…The marked increase of tissue fluorescence occurring some time after the fluorescence appeared to have ceased moving through the blood vessel walls may be due either to an increase in the fluorescence quantum yield, or to a lessening in the extent to which the fluorescence is reduced due to absorption and scattering. In the former case, the fluorescence quantum yield could increase because the polymeric conjugates have been metabolized by, for example, lysosomal proteases (Krinick et al, 1994), to free ce6 which has a greater fluorescence quantum yield (data not shown), or because the conjugates underwent a disaggregation process, similar to that which has been reported to occur with Photofrin® (Bottiroli et al, 1990). In the latter case, the increased distance of the fluorophore from the blood vessels could have reduced the scattering of excitation or emission light by erythrocytes, or absorption of excitation or emission light by haemoglobin.…”

“…These targeting species include monoclonal antibodies (Duska et al, 1997), lipoproteins (Hamblin and Newman, 1994b), microspheres (Bachor et al, 1991), liposomes (Cuomo et al, 1990) and polymers (Krinick et al, 1994). The latter may be either natural polymers such as dextran (Rakestraw et al, 1990) and polyamino-acids (Goff et al, 1991;Soukos et al, 1997) or synthetic polymers such as N-(2-hydroxypropyl)-methacrylamide (Seymour et al, 1987) and polyvinyl alcohol (Davis et al, 1993).…”

Enhanced antitumor activity of combinations of free and HPMA copolymer-bound drugs

“…Several HPMA copolymer drug conjugates underwent clinical testing, including DOX (Vasey et al, 1999) and platinates (Rademaker-Lakhai et al, 2004). The advantages of combination therapy using HPMA copolymer conjugates have been demonstrated on animal models of ovarian carcinoma (Krinick et al, 1994;Peterson et al, 1996;Shiah et al, 1999Shiah et al, , 2000Shiah et al, , 2001b. The results presented here highlight the potential applications of synergistic combinations and dose reduction for combination therapy for renal carcinoma.…”

“…The product yield was 820 mg (68%). 6 was also prepared as described previously (Kopeèek et al, 1991;Krinick et al, 1994). The conjugate was synthesized by conjugating Mce 6 to P-GFLG-ONp precursor, containing 5.1 mol% of active ester groups; M w = 22 kDa; M w /M n = 1.2.…”

“…In vivo combination chemotherapy and PDT studies on two cancer models, Neuro 2A neuroblastoma induced in A/J mice (Krinick et al, 1994) and human ovarian carcinoma heterotransplanted in nude mice (Peterson et al, 1996;Shiah et al, 2000Shiah et al, , 2001b, demonstrated that combination therapy with HPMA copolymer-bound DOX and HPMA copolymer-bound Mce 6 (mesochlorin e 6 monoethylene diamine) produced tumor cures which could not be obtained with either chemotherapy or PDT alone. Additionally, significantly lower nonspecific toxicities were observed when compared to low-molecular weight drugs.…”