PHY906, a four-herb Chinese medicine formula first described 1800 years ago, decreases gastrointestinal toxicity induced by the chemotherapeutic drug CPT-11 (irinotecan), as shown in a phase I/II clinical study. Similarly, in a murine colon 38 allograft model, PHY906 increased the antitumor activity of CPT-11 while decreasing animal weight loss caused by CPT-11. Here, we have further examined the effect of PHY906 on the intestinal toxicity caused by CPT-11 in mice. PHY906 did not protect against the initial DNA damage and apoptosis triggered by CPT-11 in the intestine, but by 4 days after CPT-11 treatment, PHY906 had restored the intestinal epithelium by promoting the regeneration of intestinal progenitor or stem cells and several Wnt signaling components. PHY906 also potentiated Wnt3a activity in human embryonic kidney-293 cells. Furthermore, PHY906 exhibited anti-inflammatory effects in mice by decreasing the infiltration of neutrophils or macrophages, tumor necrosis factor-alpha expression in the intestine, and proinflammatory cytokine concentrations in plasma. Chemical constituents of PHY906 potently inhibited nuclear factor kappaB, cyclooxygenase-2, and inducible nitric oxide synthase. Our results show that the herbal medicine PHY906 can counteract the toxicity of CPT-11 via several mechanisms that act simultaneously.

The second generation of methylenecyclopropane analogues of nucleosides 5a-5i and 6a-6i was synthesized and evaluated for antiviral activity. The 2,2-bis(hydroxymethyl)methylenecyclopropane (11) was converted to dibromo derivative 7 via acetate 12. Alkylation-elimination of adenine (16) with 7 afforded the Z/E mixture of acetates 17 + 18, which was deacetylated to give analogues 5a and 6a separated by chromatography. A similar reaction with 2-amino-6-chloropurine (19) afforded acetates 20 + 21 and, after deprotection and separation, isomers 5f and 6f. The latter served as starting materials for synthesis of analogues 5b, 5e, 5g-5i and 6b, 6e, 6g-6i. Alkylation-elimination of N(4)-acetylcytosine (22) with 7 afforded a mixture of isomers 5c + 6c which were separated via N(4)-benzoyl derivatives 23 and 24. Deprotection furnished analogues 5c and 6c. Alkylation of 2,4-bis(trimethylsilyloxy)-5-methylpyrimidine (25) with 7 led to bromo derivative 26. Elimination of HBr followed by deacetylation and separation gave thymine analogues 5d and 6d. The guanine Z-isomer 5b was the most effective against human and murine cytomegalovirus (HCMV and MCMV) with EC(50) = 0.27-0.49 microM and no cytotoxicity. The 6-methoxy analogue 5g was also active (EC(50) = 2.0-3.5 microM) whereas adenine Z-isomer 5a was less potent (EC(50) = 3.6-11.7 microM). Cytosine analogue 5c was moderately effective, but 2-amino-6-cyclopropylamino derivative 5e was inactive. All E-isomers were devoid of anti-CMV activity, and none of the analogues was significantly active against herpes simplex viruses (HSV-1 or HSV-2). The potency against Epstein-Barr virus (EBV) was assay-dependent. In Daudi cells, the E-isomers of 2-amino-6-cyclopropylamino- and 2,6-diaminopurine derivatives 6e and 6h were the most potent (EC(50) approximately 0.3 microM), whereas only the thymine Z-isomer 5d was active (EC(50) = 4.6 microM). Guanine Z-derivative 5b was the most effective compound in H-1 cells (EC(50) = 7 microM). In the Z-series, the 2-amino-6-methoxypurine analogue 5g was the most effective against varicella zoster virus (VZV, EC(50) = 3.3 microM) and 2,6-diaminopurine 5h against hepatitis B virus (HBV, EC(50) = 4 microM). Adenine analogues 5a and 6a were moderately active as substrates for adenosine deaminase.