Intracellular metabolism of the nucleotide prodrug GS-9131, a potent anti-human immunodeficiency virus agent.
GS-9131 is a phosphonoamidate prodrug of the novel ribose-modified phosphonate nucleotide analog GS-9148 that demonstrates potent anti-human immunodeficiency virus type 1 (HIV-1) activity and an excellent resistance profile in vitro. Prodrug moieties were optimized for the efficient delivery of GS-9148 and its active diphosphate (DP) metabolite to lymphoid cells following oral administration. To understand the intracellular pharmacology of GS-9131, incubations were performed with various types of lymphoid cells in vitro. The intracellular accumulation and antiviral activity levels of GS-9148 were limited by its lack of cellular permeation, and GS-9131 increased the delivery of GS-9148-DP by 76- to 290-fold relative to that of GS-9148. GS-9131 activation was saturable at high extracellular concentrations, potentially due to a high-affinity promoiety cleavage step. Once inside the cells, GS-9148 was efficiently phosphorylated, forming similar amounts of anabolites in primary lymphoid cells. The levels of GS-9148-DP formed in peripheral blood mononuclear cells infected with HIV-1 were similar to that in uninfected PBMCs, and approximately equivalent intracellular concentrations of GS-9148-DP and tenofovir (TVF)-DP were required to inhibit viral replication by 90%. Once it was formed, GS-9148-DP was efficiently retained in activated CD4(+) cells, with a half-life of 19 h. In addition, GS-9131 showed a low potential for drug interactions with other adenine nucleoside/nucleotide reverse transcriptase inhibitors, based on the lack of competition for anabolism between suprapharmacologic concentrations of GS-9148 and TVF and the lack of activity of GS-9131 metabolites against purine nucleoside phosphorylase, an enzyme involved in the clearance of 2',3'-dideoxyinosine. Together, these observations elucidate the cellular pharmacology of GS-9131 and illustrate its efficient loading of lymphoid cells, resulting in a prolonged intracellular exposure to the active metabolite GS-9148-DP.
Ray
Adrian S
AS
Department of Drug Metabolism, Gilead Sciences, Inc., 333 Lakeside Dr., Foster City, CA 94404, USA. adrian.ray@gilead.com
Vela
Jennifer E
JE
Boojamra
Constantine G
CG
Zhang
Lijun
L
Hui
Hon
H
Callebaut
Christian
C
Stray
Kirsten
K
Lin
Kuei-Ying
KY
Gao
Ying
Y
Mackman
Richard L
RL
Cihlar
Tomas
T
D000225:Adenine / Q000031:analogs & derivatives* / Q000737:chemistry / Q000378:metabolism; D019380:Anti-HIV Agents / Q000378:metabolism*; D011756:Diphosphates / Q000737:chemistry / Q000378:metabolism; D006151:Guanosine / Q000031:analogs & derivatives / Q000737:chemistry / Q000378:metabolism; D015658:HIV Infections / Q000821:virology; D015497:HIV-1 / Q000187:drug effects*; D006801:Humans; D007963:Leukocytes, Mononuclear / Q000378:metabolism* / Q000821:virology; D008213:Lymphocyte Activation; D063065:Organophosphonates / Q000737:chemistry / Q000378:metabolism; D011355:Prodrugs / Q000737:chemistry / Q000378:metabolism*; D018894:Reverse Transcriptase Inhibitors / Q000737:chemistry / Q000378:metabolism; D000068698:Tenofovir
D019380:Anti-HIV Agents; D011756:Diphosphates; C519972:GS-9131; D063065:Organophosphonates; D011355:Prodrugs; D018894:Reverse Transcriptase Inhibitors; D006151:Guanosine; D000068698:Tenofovir; C527398:GS-9148; D000225:Adenine