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Global Experts Meeting on Infectious Diseases

Tokyo, Japan

Hiroshi Ohrui

Hiroshi Ohrui

Yokohama University of Pharmacy

Title: EFdA, An Extreemely Excellent Anti-HIV Nucleosides -How it was developed and clinical results by Merck-


Biography: Hiroshi Ohrui


4’-C-Ethynyl-2-fluoro-2’-deoxyadenosine (EFdA) has attracted much attention due to its extremely excellent anti-HIV activity,  for example; 1. prevent the emergence of resistant HIV mutants,  2. over 400 times more active than AZT and several orders of magnitude more active than the other clinical reverse-transcriptase inhibitor y 2’, 3’-dideoxy-nucleoside drugs,  3. very low toxic,  4. very long acting,  5. possible use for prophylaxis, and so on.
EFdA is now under clinical investigation by Merck &  Co.  as MK-8591.
In the beginning, my general  idea for the development  of  anti-viral modified nucleosides will be presented, and then the development of EFdA will be discussed and the clinical results by Merck ill be also presented. For the design of the modified nucleoside which could solve the problems that the clinical drugs have (1. emergence of drug-resistant HIV mutants, 2. adverse effect by drugs, 3. necessity of  taking  quite a few amount of drugs), the following working hypotheses were proposed . They are (1) the way to prevent the emergence of drug-resistant HIV mutants, (2) the way to decrease the toxicity of modified nucleosides, (3) the way to provide the modified nucleoside with stability to both enzymatic and acidic glycolysis for long acting.

4’-C-substituted-2’-deoxy nucleoside (4’SdN) was designed to meet the hypotheses (1), (3), and the additional  modification of 4’SdN was performed to meet the hypothesis (2).

The details of the hypotheses and the reasons of the design of 4’SdN will be discussed.

To prevent the deamination of adenine base by adenosine deaminase,  fluorine atom was introduced at the 2-position of adenine base.

Finally, EFdA , modified at the two position (2 and 4’) of the physiologic 2’-deoxyadenosine and has  extremely excellent anti-HIV activity,  was  successfully developed.