SOLVED. Adult Thriller? Fountain of youth/longevity. Scientist looking for a research grant. Read in 1980s. [s]

[JJ]

I read this book in the 80's, it was on my mothers book shelf and I have only a few details to go on:
The cover was white (paperback), with I think a syringe on the front cover.
The main plot was a doctor/scientist looking for a gene to prolong life/looking for eternal life and had applied for a grant from some kind of institution.
An investigator from the institute offering grants gets sent to look at the claim and finds out the scientist/doctor is running an elderly home, testing the drug on patients (I think)
I remember there being a younger wife involved, possibly step children and a church
The investigator gets caught up in the community and possibly involved with the wife?
Arghhhh, it's 3am in the morning, I've spent the best part of 2 hours searching for this and this is my last hope!

[Bargle]

Maybe The Sixth Commandment by Lawrence Sanders?

Note to self: correct answer.

[JJ]

Bargle wrote: "Maybe The Sixth Commandment by Lawrence Sanders?"

Yes! Thank you, this is the best community in the world!