Drug retention and distribution after intratumoral chemotherapy with fluorouracil/epinephrine injectable gel in human pancreatic cancer xenografts.

PURPOSE: Pancreatic cancer is widespread, associated with high mortality, and rapidly fatal. Most cases are diagnosed too late for surgical treatment, and the disease responds poorly to systemic chemotherapy. Nevertheless, pancreatic cancer cells are sensitive to fluorouracil (5-FU) in a time- and dose-dependent manner, suggesting that improved retention of drug in the tumor may improve patient prognosis. In this study, we evaluated a novel drug delivery system, 5-FU/epinephrine injectable gel (5-FU/epi gel), designed to improve drug retention in tumors. METHODS: We used a BxPC-3 human pancreatic cancer xenograft model in athymic mice to examine drug levels in tumor, liver, and kidney tissue following administration of: (a) 5-FU/epi gel (30 mg 5-FU/ml) intratumorally (i.t.); (b) 5-FU solution i.t.; and (c) 5-FU solution intraperitoneally (i.p.). [(3)H]5-FU was added as a radiolabeled marker to all test formulations. Animals were sacrificed at designated times, and the tumor, liver, and one kidney from each animal were excised and processed for radioactivity analysis. Drug concentration was quantified by both storage-phosphor autoradiography (SPA) and liquid scintillation counting (LSC). RESULTS: Higher and sustained i.t. drug levels were achieved following i.t. administration of 5-FU/epi gel (SPA AUC 18.4 mM. h, LSC AUC 13.0 mM. h) compared with 5-FU solution i.t. (SPA AUC 2.02 mM. h, LSC AUC 1.92 mM. h) or 5-FU solution i.p. (SPA AUC 0.07 mM. h, LSC AUC 0.04 mM. h). Use of the 5-FU/gel system was associated with lower drug levels in liver and kidney, indicating that it produces far less systemic exposure. CONCLUSION: In the human pancreatic cancer xenografts, i.t. administration of 5-FU/epi injectable gel provided significantly higher drug and/or metabolite concentrations for extended periods than was possible with either i.t. or i.p administration of drug solution. This i.t. drug delivery system could potentially be used to treat patients with pancreatic cancer to increase tumor exposure to drug and improve the therapeutic index in comparison to systemic drug administration.

Influence of treatment sequence on efficacy of fluorouracil and cisplatin intratumoral drug delivery in vivo.

PURPOSE: The influence of treatment sequence in combination chemotherapy using fluorouracil (5-FU) and cisplatin (CDDP) was investigated in a mouse tumor model. Both drugs were formulated as therapeutic injectable gels, 5-FU/epinephrine gel and CDDP/epinephrine gel, and used intratumorally in a multiple-treatment regimen. By testing various multiple-treatment regimens, we determined optimal treatment sequences for these two injectable gels. Then we compared the antitumor responses achieved using the optimal treatment sequences for the intratumorally administered gels with the responses obtained using 5-FU and CDDP solutions administered intratumorally or systemically in the same treatment sequence. MATERIALS AND METHODS: Tumor-bearing C3H mice received a total of four injections (every 2 to 3 days from day 0 through day 7) of 5-FU solution, CDDP solution, 5-FU/epinephrine gel, or CDDP/epinephrine gel either as single agents or in various combinations and alternate sequences of solutions or gels. The delay in tumor growth was used as a study end-point. RESULTS: The results showed that local treatment (i.e., intratumoral administration) was more efficacious than systemic treatment (i.e., intraperitoneal administration) when both 5-FU solution and CDDP solution were used either alone or in combination. Further, using two drugs in combination was superior to using either drug alone. When both drugs were delivered intratumorally in the injectable gel formulations, the combination treatment sequences initiated with 5-FU/epinephrine gel were superior to sequences initiated with CDDP/epinephrine gel in delaying the tumor growth. The two sequences initiated with 5-FU/epinephrine gel (i.e., two treatments with 5-FU/epinephrine gel followed by two treatments with CDDP/epinephrine gel and the sequence of alternating 5-FU/epinephrine gel and CDDP/epinephrine gel) showed no significant difference in antitumor efficacy. Both these sequences (initiated with 5-FU/epinephrine gel) produced the longest delays in tumor growth, and > or = 50% (7 of 12) animals remained disease free at the end of the 60-day study. CONCLUSION: These studies demonstrate that significant improvement in local tumor control in mice can be achieved with a simple treatment sequence alteration of two established drugs.

Variable region-identical monoclonal antibodies of different IgG subclass directed to Pseudomonas aeruginosa lipopolysaccharide O-specific side chain function differently.

Antibodies directed to polysaccharide (PS) antigens of bacteria are crucial to host immunity to infection. The isotypes of antibodies made to PS, however, are restricted primarily to IgM and IgG1 and IgG2 in man and to IgM and IgG3 in mice. Using sequential sublining and sib selection, an IgG1 murine monoclonal antibody that has variable regions identical to those of a parent IgG3 monoclonal antibody directed to the high-molecular-weight component of the O-specific side chain of Pseudomonas aeruginosa immunotype 1 lipopolysaccharide was derived. These antibodies differed markedly in their antigen binding and effector functions. IgG3 was superior in binding to multivalent PS both in purified and whole bacterial form, fixation of the third component of complement to the bacterial surface, and opsonization of P. aeruginosa for uptake by both murine and human phagocytes. These data suggest that the IgG subclass of these murine anti-LPS antibodies is an important determinant of both avidity for multivalent antigen and biologic function.

Induction of opsonic antibodies to Pseudomonas aeruginosa mucoid exopolysaccharide by an anti-idiotypic monoclonal antibody.

Mucoid strains of Pseudomonas aeruginosa are the major pulmonary pathogens for cystic fibrosis patients. Opsonizing antibodies to the mucoid exopolysaccharide (MEP) antigen may protect animals and some cystic fibrosis patients from infection. However, MEP does not readily elicit opsonic antibodies either during chronic infection or after vaccination. To evaluate alternative means to induce opsonic antibodies, a murine monoclonal anti-idiotypic antibody directed to an opsonic monoclonal antibody specific to MEP was produced. The anti-idiotypic antibody bound to F(ab')2 fragments of the opsonic antibody, blocked binding to MEP, bound to cross-reactive idiotopes on human opsonic antibodies to MEP, and elicited MEP-specific antibodies in syngeneic and allogeneic mice. These anti-idiotype-induced, MEP-specific antibodies fixed complement to mucoid P. aeruginosa cells and opsonized them for phagocytic killing by human leukocytes. These studies demonstrate the potential utility of anti-idiotypic monoclonal antibody for generating protective immunity against bacterial polysaccharides.

Anti-idiotype-induced, lipopolysaccharide-specific antibody response to Pseudomonas aeruginosa. II. Isotype and functional activity of the anti-idiotype-induced antibodies.

We recently developed a murine anti-idiotypic mAb that functioned as a molecular mimic of the O-specific polysaccharide side chain (Ps) of Pseudomonas aeruginosa LPS in vitro, and which induced Ps-specific antibodies in syngeneic BALB/c ByJ mice. In the current studies, we demonstrate that these anti-Id-induced, Ps-specific antibodies fix complement to the bacterial cell surface, and protect neutropenic mice from fatal P. aeruginosa sepsis. The isotypic distribution of the anti-Id-induced antibodies, however, resembles the restricted pattern (IgM and IgG3) seen after administration of purified Ps to mice. The immunogenicity and number of isotypes of Ps-specific antibody produced could be enhanced by conjugating the anti-Id to keyhole limpet hemocyanin. Finally, the anti-Id administered before immunization with purified Ps, primed BALB/c ByJ mice for production of other Ps-specific antibody isotypes (IgG1). These studies show that this anti-Id induces functional anti-Ps antibodies in syngeneic mice, and when used in conjugate form or as a priming agent before Ps immunization, yields an antibody response consistent with "T cell dependence." These immunization strategies may be useful for the induction of polysaccharide-specific antibodies in man.

Anti-idiotype-induced, lipopolysaccharide-specific antibody response to Pseudomonas aeruginosa.

Antibody directed to the O-specific polysaccharide (Ps) side chain of Pseudomonas aeruginosa LPS provides immunotype-specific protection against infection by virtue of enhancing opsonophagocytosis. We have developed a syngeneic anti-idiotypic antibody (mAb2) directed to a functionally active monoclonal immunotype 1 Ps-antibody (mAb1). The mAb2 performed as a molecular mimic of Ps as evidenced by 1) blocking of mAb1/mAb2 interaction by Ps, 2) blocking of mAb1/Ps binding by mAb2, 3) cross-species binding of mAb2 to human Ps antibodies from individuals immunized with the same immunotype 1 Ps, and 4) induction of anti-LPS antibody by immunization with mAb2 in syngeneic mice. Our studies thus show that an anti-idiotypic antibody may functionally mimic the O-polysaccharide of P. aeruginosa LPS, and bind to cross-reactive Id present in human Ps antibodies. We have further shown that this anti-idiotypic antibody induces anti-LPS antibody when used as an Ag in syngeneic mice, suggesting that this approach may eventually be used to successfully immunize humans.