Abstracts Vol. 1 [International Conference on AIDS (11th: 1996: Vancouver, Canada)]

Track A: Basic Science

Mo.A.1076 - Mo.A. 1081

Mo.A. 1076
2'-B-FLUORO-2',3'-DIDEOXYADENOSINE (F-DDA):A NEW ANTI-HIV CLINICAL
DRUG CANDIDATE
ohns, David G, Driscoll J. laboratory of Medicinal Chemistry, Natinil (Lanceri Institute,
DBS, NIH, Bethesda, MD USA
Objective: To characterize the pharmacological, toxicological and chemical proper ties of the
2 '--fluoro analog of the anti-HIV agent 2',3'-dideoxyadenosine.
Methods: F ddA was synthesized in this laboratory and its anti-HIV activity determined in a
variety of in vitro assay systems,. including ATH8 cells, monocyte/macrophages. and PHA/PBM
cells. Activity was also determined vs. viral clinical isolates resistant to AZ1, ddi and ddC, and
against viral mutants iresistant to TIBO and other non-nucleoside RT inrhibrtor s. In addition,
the antiviral activity in combination with AZT and with agents affectin host-cell metabolism
(hydroxyurea, ribavirin, 2'-deoxycoformycin) was ascertained. In viva, I ddA activity was
determined in the hu-PBL SCID mouse model. In biochemical studies, the 5'-phosphorylation and the deamination of the drug were determined in human I cell lnes by ionexchange HPL C. utilizing 3H-labeled drug.
Results: The potency of F-ddA against HIV I iii vitro is similar to that of the non fluorinated
analogs ddA and ddl. F ddA is not cross-resistant to AZT, ddC, ddl, or non nucleoside RT
inhibitors.The combination I -ddA/AZT is synergistic, and F-ddA activity is enhanced several fold by hydroxyurea and ribavirin. In vivo, F-ddA is more active than AZ1T when administered orally in the SCID mrouse model. F-ddA is a substrate for adenosine deaminase, yielding the corresponding inosine derivative (also an active anti-HIV agent), which is phosphorylated by a 5'-nucleotidase, and then anabolized to F-ddATP In contrast to ddl, F-ddl is not
cleaved by punrne nucleoside phosphorylase. Chemically F-ddA, unlike ddA or ddl. resists
acid cleavage, and thus can be administered orally without buffering. As an inhibitor of mitehord r ial DNA synthesis, F-ddA is > 20,000 X less toxic than ddC.
Conclusions: Ii view of its pharmacological activity lack of cross resistance, and chemical
stability, f ddA appears to exhibit properties favorable for clinical study as an anti HIV
agent, and will thus shortly be entering Phase 1/11 trial for further asses sment.
D. G. Johns. Bldg. 37, Rm. 5B22, NCI, Nat. Institutes of Health Bethesda, MD) USA 20892 -4255 TEL: [phone] FAX: [phone] or 301-402-2275
Mo.A. 1077
L-743,726 (DMP-266):ANOVEL, HIGHLY POTENT NONNUCLEOSIDE INHIBITOR OF
THE HUMAN IMMUNODEFICIENCY VIRUS TYPE I REVERSE TRANSCRIPTASE.
Young, Steven D., etal. Merck Research Laboratories, West Point, PA 19486 USA
fThe clinical benefit of the human immunodeficiency virus type I (HIV I) nonnucleoside
reverse transcriptase (RT) inhibitors (NNRTI's) is limited by the rapid selection of inhibitorresistant viral variants.We believe the clinical utility of this class of anti-HIV agents may be
enhanced if a compound expressing both high levels of antiviral activity and a superior
pharmacokinetic profile were found. Accordingly we developed a new class of NNRTI's, the,4 dihydro-2H-3, I-benzoxazin-2-ones. A member of this class, L 743,726 (DMP F'-266) was
chosen for clinical evaluation because of its high level of antiviral potency and oral bioavailabilityThis compound is a potent inhibitor of wild-type HIV I RT (Ki 2.93 nM) and
exhibits a 95% inhibitory concentration of 1.5 nM for the inhibition of HIV I replicative
spread in cell culture. L-- 743,726 is capable of inhibiting, with 95% inrhibitory concentrations
of <_ 1.5 pM, a panel of NNRTI- resistant mutant viruses, each of which expressed a single
RT amino acid substitution. Derivation of virus with notably reduced susceptibility to the
inhibitor required prolonged cell culture selection and was mediated by a comrbination of at
least two RT amino acid substitutions in the viral reverse transcriptase. Inr vivo studies of L743,726 in rats, monkeys and a single chimpanzee demonstrated the compound s potential
for good oral bioavailability and pharmacokinetics in man.The discovery rand preclinical evaluation of this compound will be presented.
S. D.Young,WP26-410, Merck Research Laboratories West Point, PA 19486
tel: [phone]
Mo.A.1078
SUPPRESSION OF BOTH WILD-TYPE AND DRUG-RESISTANT HIV- I BY
COMBINATION OF THYMIDYLATE SYNTHASE INHIBITORS WITH AZT OR D4T
Gao, Wen-Yi",Tanaka M*, Ahluwalia GS**, Johns DG*, Mitsuya H'.W F xptl. Retrovirol. Sect.
& "Lab. Med. Chem., National Cancer Institute, NIH, Bethesda, MD USA
Objective: To develop a non-discriminative strategy for the inhibition oft replication of both
wild-type and drug-resistant HIV- I.
Methods: The dependence of proviral DNA replication by ell HIV I strains on host cell
dNTPs, including dTF,was selected as the target.The antiviral activities of orifniatrlions of low
concentrations of the thymidylate synthase inhibitors 5-FU or FUdR with AZT or D4T were
studied in PHA/PBM cells.Two types of HIV I strains were used: a hnial isolate from a patient
with advanced HIV I infection prior to antiviral therapy, and recombinant muliple d r ui-resis
tant HIV- I variants, including HIV- I Q15 I M.The Q I5IM mutation occurred dun AZT/ddC
combination therapy, and conferred HIV I resistance to AZT, D4T ddC, ddI and ddG.
Results: Both the HIV-l I clinical isolate and the drug resistant mutant were susceptible to
the combination of low concentratons of thyrsidylate synthase irfhibitor s with either AZT
or 1348 In the presence of 2 pM 5-FU, the antiviral activities of AZT Fnd D4 against the
HIV I clinical isolate were enhanced by 36 and 79-fold respectively At the same bF U concentration, the,ctivity of AZ] against HIV QI 151 M was enhanced by l0 fid No cyto
toxicity was observed at these drug levels. Mechanism studies showed the enhancement to
be due to seversible inhibition of de nov synthiesis of dl-P by either sit the Ilrymidylate
synthase inhibitors, together with consequent increased phosphoryation of AZT or [4T by
thymidine kinase, in enzyme under feedback regulatory control fry FTTPf
Conclusions: Since the selective advantage given by anti-HIV I drug treatment,- replica
tion of drug resistant mutants is the major cause of failure of dIV monotherapy and since
drug-resistanre is a consequence of rapid sirus turnover and a resurtarr firs sporntaneous
rnutation fiequenry, the combination of dIIP-depleting agents witht AZT or D4I rray offer
a non-discnrmrnate strategy for the inhibition of drug-resistant as well as wild-type HIV- I at
both the prereplcational and 5eplicational stages.
Dr Wen-Yi Gao, Bldg. 10, Rm 5A24, Nat. Cancer Inst., NIH, Bethesd, MD USA 20892.Tel:
30 I -496-9239; FAX: [phone]

Mo.A. 1079
LYMPHATIC DISTRIBUTION OF 2',3'-DIDEOXYINOSINE (ddl) AFTER ADMINISTRATION OF PHOSPHOLIPID PRODRUG IN MICE.
Manouilov K.K.*, Xu Z.-S.*, Boudinot F.D.*, Schinazi R.F.*-*, Chu C.K.*. 'University of
Georgia, Athens, GA, USA;**"Emory University /V.A., Atlanta, GA, USA.
Objective: Previously it was shown that administration of phospholipid prodrugs of AZT and
AZdU resulted in increased exposure of the nucleosides in the lymphatic system compared
to administration of parent compounds (Manouilov et l. 1995, Antiviral. Chem. Chlemotrer. 6,
230). In the search for prodrugs of ddl with potential for increasing lymphatic delivery of ddl,
dipalmitoy-phosphatidyl-ddl (DPP-ddl) was synthesized and evaluated in mice.
Methods: The pharmacokinetics of ddl in serum, neck, axiltary and mesenteric lymph nodes
(LN) were evaluated in female NIH Swiss mice. ddl (100 mg/kg) or DPP-ddl (equivalent to
100 mg/kg of ddl) were administered intravenously (iv) and orally (po). Concentrations of
ddl were determined by HPLC. Pharrmacokinetic parameters were estimated by
area/moment analysis.
Results: After iv administration of ddl, the serum ddl concentration at 5 min was 146 pg/mI
and half-life was 0.26 h.The AUC in serum was 42.5 mg/I-h. Accumulation of ddl in LN, in
terms of AUC, was 81-92% of that in serum and was higher than that of AZT (25-77%)
and AZdU (44 82%). After po administration of ddl following aluminum hydroxide gel, the
bioavaiability of ddl was 15%. AUCs in L.N were 150-230% of the serum value.The half-life
of ddl in serum was 0.3 h and that in LN was 2-3 fold higher:
Iv admirnistration of DPP-ddl resulted in 46% bioavailability of ddl, but exposure of LN to
the nucleoside was similar to that when ddl itself was given (availability in different LN was
75-II 0%).The maximum concentration of ddl in serum of 6.5 pg/ml was observed at I h.
Half-lives of ddl in serum and LN were extended 5-8 fold. Bioavailability of ddl after po
administration of DPP-ddl was 4%, but accumulation of ddl into LN was 250-320% compared to serunm.
Conclusions: Compared to AZT and AZdU, ddl accumulated to a greater extent in LN.
The phospholipid prodrug of ddl further enhanced the lymphatic delivery of ddl.
C.K. Chu, #374 Med. Chem. College of Pharmacy University of Georgia.Tel: [phone]
FAX (706) 5,12 538 I e-mail: DChu@r-x. UGA.edu
Mo.A. 1080
ANTIVIRAL ACTIVITY AND PHARMACOKINETICS OF T-20,AN AMPHIPATHIC
HELICAL PEPTIDE DERIVED FROM GP4I.
D. M. Lambert, M. Ross Johnson, P L. Black*, M. A. Ussery*,TVenetta, E. DiMassimo, S. Barney
et at. Trmeris, Inc., Research Triangle Park, NC. 27709 and *U.S.F.D.A., Rockville, MD 20857
T-20 (pentafuside, DP-178), a 36-mer synthetic peptide derived from the HIV- I gp41I transmembrane protein, is a selective and potent inhibitor of HIV- I infection (IC50=80ng/mnl)
and fusion (IC50=1ng/ml) in vitro.T-20 appears to block the transition of gp4 I to it fusogenic
state during the infection process and during cell to cell fusion by binding to the coiled coil
(DP-107) region of the protein.Tlo evaluate T-20 as a potential lead compound for clinical
investigationr,, we assessed the ex vivo stability of T-20 in rodent and human plasma. No
detectable degradation was observed when T-20 was incubated in plasma at 37"C for 4
hours. Pharmnacokinetic studies in rodents (4 mg/kg, i.v. bolus) revealed a surprisingly long
half-life in crculation (t /2=2.4 hr), with sustained levels above the IC50 for at least 6 hr:
Rodent studies indicate that T-20 exhibits a distribution phase half-life of 15 minutes following s.c. aind i.r. administration.The elimination phase half-life is approximately 2.5 hours.
Studies in primates indicate that T-20 exhibits an elimination phase half-life in excess of 3
hours following i.v.. i.m., and s.c. administration.The relative bioavailability ofT-20 is greater
than 70% when given by i.m. or s.c. administration. Plasma AUC varies in direct proportion
with amount of drug administered by s.c injection. Plasma levels of T-20 in excess of the inr
vitro IC50 for ell fusion and infectivity are maintained for 12 hours following administration
of a single 0.4 mg/kg bolus dose. Results of in vivo studies with 1-20 in the HuPBMC SCID
mouse model of infection will be discussed.These results support the potential therapeutic
efficacy of this novel class of antiviral agents and suggest thatT-20 is a candidate for clinical
nvestig ation in the treatment of HIV- I infection.
U.M. Lambert, P O. Box 13963, Research Triangle Park, North Carolina 27709, USA.
Telephone: [phone] Fax [phone]
Mo.A.108 I
DESIGN. SYNTHESIS AND SAR OF DIHYDROPYRONE SULFONAMIDE
NON-PEPTIDIC HIV PROTEASE INHIBITORS
Skulnick-farvey l, Johnson, PD., Aristoff, PA,Turner, S.R., Strohbach, J.W.,Tommasi, R.A.,
Thaisrivongs. S., Skaletzky L.L., Judge,TM., Morris, J.K., Castle,TM., Seest, E.P., Dotak, L.A.,
Horng, M M., Lynn, J.C..Tomich, PK., Hinshaw, R.R., Pagano. PJ., Chong, K.T Pharmacia and
Upjohn, Inc., Kalamazoo, MI, USA
Objectives: To design and synthesize a series of dihydropyrone sulfonamides with impr oved
HIV antiviral and protease inhibition based on the previously disclosed pyrone templates U99499 aid U- 103017.
Methods: The reaction between a heteroaromatic sulfonyl chloride and a chirat amino dihydropyran-2 one gave an enantiomericaly pure dihydropyrone sulfonamide with picomolar
activity aiainst HIV protease and nanomolar antiviral activity in cell culture.
Results: The vwuious chiral dihydropyran-2-one sulfonamides exhibited antiviral and HIV
protease activity which could be predicted by their sulfonamide substitution patterns. In
contrast to thre U 103017 template, the antiviral activity of the dihydropyrone sulfonamides
was not greatly decreased in the presence of added plasma proteins.
Conclusions: It ws possible to pepare potent anti--HIV dihydropyrone sulfonamides which
exhibited both HIV protease inhibition and cel culture antiviral activity similar to the peptidir intibitors. It was also possible to develop a reliable SAR f-rom the dihydropyran-2-one
sulfonaneu des synthesized.
H. I. Skulnirk, 7254 209-648, Pharmaci & Upjohn, Inc., Ralarazoo, MI 49001, USA;
Phone [phone]: Fax [phone] email [email protected]

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