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Antimicrobial Agents and Chemotherapy, August 1999, p. 1888-1894, Vol. 43, No. 8
Department of Biologic and Materials
Sciences,
Received 1 December 1998/Returned for modification 23 February
1999/Accepted 13 May 1999
Based upon a prior study which evaluated a series of nonnucleoside
pyrrolo[2,3-d]pyrimidines as inhibitors of human
cytomegalovirus (HCMV), we have selected three active analogs for
detailed study. In an HCMV plaque-reduction assay, compounds 828, 951, and 1028 had 50% inhibitory concentrations (IC50s) of 0.4 to 1.0 µM. Similar results were obtained when 828 and 951 were
examined by HCMV enzyme-linked immunosorbent assay
(IC50s = 1.9 and 0.4 µM, respectively) and when 828 was tested in a viral DNA-DNA hybridization assay
(IC50 = 1.3 µM). In yield-reduction assays with a
low multiplicity of infection (MOI), all three compounds caused
multiple log10 reductions in virus titer, and the
activities of these compounds were comparable to the activity of
ganciclovir (GCV; IC90 = 0.2 µM). In contrast to the
reduction of viral titers by GCV, the reduction of viral titers by 828, 951, and 1028 decreased with increasing MOI. Cytotoxicity in human
foreskin fibroblasts and KB cells ranged from 32 to >100 µM. In
addition, 828 (the only compound tested) was less toxic against human
bone marrow progenitor cells than GCV. Time-of-addition and
time-of-removal studies established that the three pyrrolopyrimidines inhibited HCMV replication before GCV had an effect on viral DNA synthesis but after viral adsorption. Compound 828 was equally effective against GCV-sensitive and GCV-resistant HCMV clinical isolates. Combination studies with 828 and GCV showed that the effects
of the two compounds on HCMV were additive but not synergistic. Taken
together, the data indicate that these pyrrolopyrimidines target a
viral protein that is required in an MOI-dependent manner and that is
expressed early in the HCMV replication cycle.
0066-4804/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
Nonnucleoside Pyrrolopyrimidines with a Unique
Mechanism of Action against Human Cytomegalovirus


*
Corresponding author. Mailing address: School of
Dentistry, University of Michigan, 1011 N. University Ave., Ann Arbor,
MI 48109-1078. Phone: (734) 763-5579. Fax: (734) 764-7406. E-mail: jcdrach{at}umich.edu.
Present address: Microcide Pharmaceuticals, Inc., Mountainview,
CA 94043.
Present address: Lake Erie College of Osteopathic Medicine, Erie,
PA 16509.
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