title: Combination chemotherapy: interaction of 5-methoxymethyldeoxyuridine with adenine arabinoside, 5-ethyldeoxyuridine, 5-iododeoxyuridine, and phosphonoacetic acid against herpes simplex virus types 1 and 2.
abstract: The antiviral activity of 5-methoxymethyl-2'-deoxyuridine (MMUdR) was compared with that of 5-iodo-2'-deoxyuridine (IUdR), 5-ethyl-2'-deoxyuridine (EtUdR), adenine arabinoside (Ara-A), and phosphonoacetic acid (PAA) against herpes simplex virus type 1 (HSV-1) and type 2 (HSV-2). MMUdR was more potent than Ara-A and PAA but less active than EtUdR and IUdR against HSV-1 in rabbit kidney (RK-13) cells. In Vero cells, the antiviral activities of MMUdR, Ara-A, and PAA against HSV-1 were of the same order of magnitude. The antiviral potency against HSV-2 varied with the strain of virus used. All strains of HSV-2 were markedly inhibited by EtUdR and IUdR and to a lesser degree by PAA. However, considerable variation was noticed in the susceptibility of HSV-2 strains to Ara-A and MMUdR. Interaction of MMUdR with Ara-A, EtUdR, IUdR, and PAA was investigated by the method of response isobolograms. MMUdR showed synergistic activity in combination with Ara-A and PAA but antagonistic activity in combination with EtUdR and IUdR against herpesviruses. Minimum toxic dose (concentration required to produce definite evidence of microscopic cytotoxicity in rapidly growing RK-13 cells) was determined for each compound and was found to be 512, 172, 64, 8, and less than 0.5 microgram/ml for MMUdR, PAA, Ara-A, EtUdR, and IUdR, respectively. MMUdR was found to have the maximum antiviral index against HSV-1 (512) and HSV-2 strains X-265 (102) and  ATCC (85). Antiviral index was defined as the minimum toxic dose divided by the dose that reduced plaque numbers by 50%.
mesh_terms: D000818:Animals; D000998:Antiviral Agents / Q000008:administration & dosage / Q000494:pharmacology* / Q000633:toxicity; D003857:Deoxyuridine / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004352:Drug Resistance, Microbial; D004357:Drug Synergism; D004359:Drug Therapy, Combination; D005260:Female; D006561:Herpes Simplex / Q000188:drug therapy; D007065:Idoxuridine / Q000008:administration & dosage / Q000494:pharmacology; D009154:Mutation; D010746:Phosphonoacetic Acid / Q000008:administration & dosage / Q000494:pharmacology; D011817:Rabbits; D018139:Simplexvirus / Q000187:drug effects*; D014740:Vidarabine / Q000008:administration & dosage / Q000494:pharmacology
chemical_list: D000998:Antiviral Agents; C024722:5-methoxymethyl-2'-deoxyuridine; D014740:Vidarabine; D007065:Idoxuridine; D010746:Phosphonoacetic Acid; D003857:Deoxyuridine