Synergistic anti-tumor activity of a novel immunomodulator, BCH-1393, in combination with cyclophosphamide

N,N-dimethylaminopurine pentoxycarbonyl D-arginine (BCH-1393) is a novel low molecular weight synthetic immunomodulator that has been shown to significantly stimulate cytotoxic T-lymphocyte responses both in vitro and in vivo (Zacharie B, Gagnon L, Attardo G, Connolly TP, St-Denis Y, Penney CL. Synthesis and activity of 6-substituted purine linker amine immunostimulants. J. Med. Chem. 1997;40:2883-94). Prompted by this evidence, we extended evaluation of BCH-1393 for anticancer activity in syngeneic mouse experimental tumor models. Consistent with previous findings, in vitro assessment of BCH-1393 activity demonstrated a significant increase in the CTL responses in the range of 10(-9)-10(-5) M. Treatment of mice with four consecutive daily intraperitoneal injections at 25 and 50 mg/kg resulted in a significant increase of the relative percentage of blood CD4+, CD8+, NK and monocyte subsets without any evidence of toxicity. In vivo anti-tumor activity of BCH-1393 was evaluated, either alone or in combination with subtherapeutic doses of cyclophosphamide (Cy), against weakly immunogenic mouse breast carcinoma DA-3 and strongly immunogenic colon adenocarcinoma MC38. Daily intraperitoneal injection of BCH-1393 at 50 mg/kg alone was well tolerated but produced a relatively weak anti-tumor effect in both tumor models. However, a significant inhibition of tumor outgrowth and suppression of established tumor growth was observed when BCH-1393 was administered in combination with subtherapeutic doses of Cy. Combination treatment of 50 mg/kg BCH-1393 with 100 mg/kg Cy (given as single intravenous bolus injection) starting 2 days prior to DA-3 tumor cell inoculation prevented tumor outgrowth in 70-80% of treated mice. In the remaining 20-30% of mice that had developed tumors, a nearly complete (90%) tumor growth inhibition was observed at days 22-24 post tumor implant. In the MC38 tumor model, combination treatment of established tumors with BCH-1393 and Cy (CTX) at 50 mg/kg resulted in a significant delay in tumor growth compared to CTX treatment alone. The observed concomitant anti-tumor activity of BCH-1393 with cyclophosphamide warrants further investigation of this immunomodulator as an adjunctive treatment of cancer.

Thioamides: synthesis, stability, and immunological activities of thioanalogues of Imreg. Preparation of new thioacylating agents using fluorobenzimidazolone derivatives

Imreg (Tyr1-Gly2-Gly3) is a well-known immunostimulant. However, it possesses a short half-life. Stabilized analogues of Imreg were prepared by a regioselective insertion in which peptide bonds at position 1,2 or 2,3 were replaced by thioamide linkages. This was achieved by using new thioacylating agents based on thioacyl-fluoro-N-benzimidazolone. The synthesis and properties of these reagents are described herein. This peptide modification enhanced significantly the half-life of the thioanalogues relative to Imreg in blood. The thioanalogues and Imreg were tested in vitro in T and B cell proliferation assays and for their ability to stimulate cytotoxic T-lymphocytes (CTLs). Only thiotyrosyl glycyl glycine 11 displayed some activity as evidenced by a weak stimulation of CTLs. On the basis of this activity and the increased stability, an in vivo immunological evaluation was undertaken. Immunophenotyping of 11 revealed a significant increase in activated CTL and NK cell populations in the spleen. This expansion was also accompanied by a significant stimulation of NK cells and the B cell proliferative response. Thioanalogues of Imreg were generally nontoxic, as exemplified by 11. The latter is a promising immunostimulant which may be targeted for cancer and viral infections, where CTLs and NK cells play an important role, or as a vaccine adjuvant where stimulation of antibody-producing B cells is important.

Synthesis and activity of dipeptides, linked to targeting ligands, as specific NK cell enhancers

Water soluble analogues of the lipophilic immunostimulant, octadecyl D-alanyl-L-glutamine, BCH-527, were synthesized and evaluated for the ability to stimulate natural killer (NK) cells. One of these compounds in which the octadecyl chain of BCH-527 was replaced with a shorter chain alcohol, 6-(D-alanyl-L-glutaminylamino)hexan-1-ol, 9, displayed an in vitro stimulation of NK cells comparable to that of interleukin 2 (IL 2). However, when the hydroxyl of 9 was linked to L-fucose to yield 1-beta-[6-(D-alanyl-L-glutaminylamino)hex-1-yl]-L- fucopyranose (BCH-2537, 1), the observed stimulation of NK cells was greater than that observed with IL 2. Further evaluation of these compounds revealed that the improved in vitro activity of BCH-2537 was more pronounced in vivo. That is, while both compounds significantly increased splenic NK cells, only BCH-2537 significantly increased the activity of these cells in vivo. In terms of a structure-activity relationship, NK cell activity was sensitive to minor structural modifications. It was influenced by conservative substitutions within the dipeptide, the length of the hydrocarbon chain, and the functionality at the end of the chain. No other compound enhanced NK cell activity to the extent exhibited by BCH-2537, although a few were equipotent to 9.

Enhancement of human neutrophil survival and activation by TGF-beta 1

Transforming growth factor beta (TGF-beta) is a multifunctional growth factor which promotes the inflammatory process. We have investigated the effect of TGF-beta 1 on neutrophil survival, recruitment and activation. These last steps are essential for their participation in the inflammatory response. Our results demonstrate that TGF-beta 1 at a concentration of 20-40 ng/ml is a potent neutrophil chemotactic factor. The chemotactic activity induced by TGF-beta 1 is greater than that induced by fMLP (10(-8) M). Furthermore, TGF-beta 1 (20-30 ng/ml) induces neutrophil activation demonstrated by an increase of respiratory burst and phagocytosis. Finally, TGF-beta 1 also enhances human neutrophil survival (43 to 93%) at concentrations as low as 2 to 20 ng/ml. This study provides evidence that TGF-beta 1 is capable of recruiting and activating neutrophils at inflammatory sites and enhances their survival.