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Comment by ksherlock | Hacker News Reader

Wikipedia says:

In 2024, lenacapavir was named the "2024 Breakthrough of the Year", citing its "astonishing 100% efficacy" in one large efficacy trial in women to prevent HIV and "99.9% efficacy in gender diverse people who have sex with men,"

https://en.wikipedia.org/wiki/Lenacapavir

It's curious that the article (and wikipedia) specifically refer to sexual acquisition.

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Maybe the other routes simply weren't tested for. Sex is how most people get HIV, so it makes sense to start from here. The second most common is by sharing needles, usually by drug addicts, and I can't think of an ethical way of doing a trial in such conditions. The rest is mother-child transmission, which is irrelevant as the drug is not intended for fetuses, and the odd accident which is probably too uncommon to make meaningful statistics.

Wouldn't sexually active people who have sex with men be the primary market? It makes sense this would be the focus of the drug's development.

They may also have issues trying to conduct robust clinical trials with IV drug abusers. If a subject entered rehab or were incarcerated for a period of the trial, would that invalidate their data? I don't know enough about the subject but it intuitively feels like it could present a real challenge.

Prep has been studied for IV drug users. It works, enough that it is recommended, but is much less effective. IV drug use is a massively more efficient transmission route than any type of sexual contact.

>IV drug use is a massively more efficient transmission route than any type of sexual contact.

Yes, and people who take IV drugs are much less likely than men who have sex with men in general to take a pill daily.

Asking here instead of searching, for conversational purposes:

In the 90s, some STD training I took said it was highly unlikely for otherwise healthy bio women to contract HIV from a man (ie compared to sex trafficked women in poor health), with the claim that vaginal sex is less susceptible to micro tearing that allows easy transmission than anal sex is.

I didn’t really question this at the time because it seemed plausible and I believed the people who were telling us this. (Note: this was in a medical context, not someone trying to scare us.) Is there any credibility to that idea now that we have more data, and hopefully leased biased science than we had in the 80s?

It's true that it's less likely, but calling it "unlikely" is grossly irresponsible. Yes, the chance is only 1-2%, but that's per vaginal sexual encounter. (And it's also "only" 20% for anal.)

https://stanfordhealthcare.org/medical-conditions/sexual-and...

https://pmc.ncbi.nlm.nih.gov/articles/PMC3412216/

That doesn't match what the top study says: 1.4% for anal and 0.08% for vaginal.

> The analysis, based on the results of four studies, estimated the risk through receptive anal sex (receiving the penis into the anus, also known as bottoming) to be 1.4%.

> It is estimated the risk of HIV transmission through receptive vaginal sex (receiving the penis in the vagina) to be 0.08% (equivalent to 1 transmission per 1,250 exposures).

Ah, you're right. I pulled a totally unrelated statistic. Complete nonsense to say that it's unlikely for vaginal sex.

In the fog of the day, you can understand why 1 transmission per 1,250 occurrences qualified as unlikely. Female prostitutes were self-reporting that they didn't use condoms and weren't showing symptoms. Meanwhile the disease decimated the gay male population which is why it was called GRID ("Gay-Related Immune Deficiency"). It was a complicated and horrible time and the data really wasn't there.

Yeah, agreed. That was the takeaway 3 decades ago, and I only bring it up no out of curiosity of how erroneous that turned out to be. I’d hope no one would describe it that way today.

    Receptive anal 1.4%
    Insertive anal 0.06% - 0.62%
    Receptive vaginal 0.08%
    Insertive vaginal 0.04%

Seems to still be the case..

[0] https://stanfordhealthcare.org/medical-conditions/sexual-and...

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