Metabolism, pharmacokinetics, tissue distribution, and stability studies of the prodrug analog of an anti-hepatitis B virus dinucleoside phosphorothioate.
The alkoxycarbonyloxy dinucleotide prodrug R(p), S(p)-2 is an orally bioavailable anti-hepatitis B virus agent. The compound is efficiently metabolized to the active dinucleoside phosphorothioate R(p), S(p)-1 by human liver microsomes and S9 fraction without cytochrome P450-mediated oxidation or conjugation. The conversion of R(p), S(p)-2 to R(p), S(p)-1 appears to be mediated by liver esterases, occurs in a stereospecific manner, and is consistent with our earlier reported studies of serum-mediated hydrolytic conversion of R(p), S(p)-2 to R(p), S(p)-1. However, further metabolism of R(p), S(p)-1 does not occur. The presence of a minor metabolite, the desulfurized product 10 was noted. The prodrug R(p), S(p)-2 was quite stable in simulated gastric fluid, whereas the active R(p), S(p)-1 had a half-life of <15 min. In simulated intestinal fluid, the prodrug 2 was fully converted to 1 in approximately 3 h, whereas 1 remained stable. To ascertain the tissue distribution of the prodrug 2 in rats, the synthesis of (35)S-labeled R(p), S(p)-2 was undertaken. Tissue distribution studies of orally and intravenously administered radiolabeled [(35)S]2 demonstrated that the radioactivity concentrates in the liver, with the highest liver/plasma ratio in the intravenous group at 1 h being 3.89 (females) and in the oral group at 1 h being 2.86 (males). The preferential distribution of the dinucleotide 1 and its prodrug 2 into liver may be attributed to the presence of nucleoside phosphorothioate backbone because phosphorothioate oligonucleotides also reveal a similar tissue distribution profile upon intravenous administration.
Spring Bank Pharmaceuticals, Inc., S-7, 113 Cedar St., Milford, MA 01757, USA.
John E
JE
Coughlin
Rajendra K
RK
Pandey
Seetharamaiyer
S
Padmanabhan
Kathleen G
KG
O'Loughlin
Judith
J
Marquis
Carol E
CE
Green
Jon C
JC
Mirsalis
Radhakrishnan P
RP
Iyer
D000284:Administration, Oral; D000818:Animals; D000998:Antiviral Agents / Q000737:chemistry / Q000378:metabolism / Q000493:pharmacokinetics; D001711:Biotransformation; D002851:Chromatography, High Pressure Liquid; D015195:Drug Design; D004355:Drug Stability; D005260:Female; D005750:Gastric Juice / Q000737:chemistry; D006515:Hepatitis B virus / Q000187:drug effects*; D006801:Humans; D066298:In Vitro Techniques; D007275:Injections, Intravenous; D007419:Intestinal Secretions / Q000737:chemistry; D008297:Male; D013058:Mass Spectrometry; D008862:Microsomes, Liver / Q000201:enzymology / Q000378:metabolism; D008954:Models, Biological; D015394:Molecular Structure; D054735:Phosphorothioate Oligonucleotides / Q000737:chemistry / Q000378:metabolism / Q000493:pharmacokinetics; D011355:Prodrugs / Q000737:chemistry / Q000378:metabolism / Q000493:pharmacokinetics; D051381:Rats; D017207:Rats, Sprague-Dawley; D013237:Stereoisomerism; D014018:Tissue Distribution
D000998:Antiviral Agents; D054735:Phosphorothioate Oligonucleotides; D011355:Prodrugs