The Pill in Your Medicine Cabinet That's Quietly Rewriting Cancer Research
David Sinclair told Joe Rogan he takes Viagra every day for his hair. The real story is what the same drug class is doing to cancer.
David Sinclair went on Joe Rogan recently and admitted he takes a low daily dose of tadalafil, the generic behind Cialis. His stated reason was hair. That's the punchline everyone will remember. It's not the part I can't stop thinking about.
The same drug class Sinclair jokes about for scalp perfusion is turning up in cancer research that has nothing to do with vanity. Tadalafil appears to strip away the immune camouflage tumors use to hide from the body's own defenses. Sildenafil, the closely related compound behind Viagra, appears to trap cholesterol inside cancer cells in a way that limits how far the disease can spread. Two drugs the world has spent thirty years associating almost entirely with the bedroom are showing up in immunology and metabolism data that looks nothing like what they were built for.
What the Research Actually Shows
This isn't a fringe theory. Researchers at the University of Miami first showed in a 2015 clinical trial that tadalafil could reduce the population of immune-suppressing cells that head and neck cancers use to evade the body's T-cells, restoring the immune system's ability to find and attack the tumor. That work has continued for a decade since, through additional trials pairing tadalafil with immunotherapy drugs in patients with recurrent disease.
Then, this past July, a team at the Weizmann Institute of Science published a separate finding in the journal Cancer Research. They found that sildenafil traps cholesterol inside a cancer cell's internal recycling system, cutting off the supply cancer cells rely on to move, spread, and metastasize. Across mouse models and human cancer cell lines, the effect held. When researchers layered in cholesterol-lowering statins alongside sildenafil, the anti-metastatic effect got stronger. Health records from millions of patients in Israel showed a survival benefit among men already taking the drug, more pronounced in those also on statins.
Most side effects were never side effects. They were just the parts of the system nobody had gotten around to measuring yet.
Why This Gets My Attention
I didn't get into venture and growth investing because I love reading FDA filings. I got into it because I like watching what happens when smart people refuse to accept the label something was given thirty years ago. A drug built for blood pressure became a drug for erectile dysfunction. Now the same drug family might be doing meaningful work in oncology, and the mechanism, blood flow and nitric oxide signaling, was hiding in plain sight the entire time.
The hair angle is still mostly mechanistic. Sinclair's daily habit hasn't been run through a placebo-controlled trial for scalp regrowth, and I'm not going to pretend it has. The cancer data is a different matter. It's real, published, and peer reviewed, even if it's early. Head and neck cancer trials are years ahead of most other indications. The metastasis research is newer and needs more human trials before anyone should treat it as settled. For anyone who has sat with a cancer diagnosis, in their own life or a family member's, I know "early and promising" isn't the same as "available." It's worth being honest about that distinction, even while the direction of the research is genuinely exciting.
What I keep coming back to is how much of biology, and honestly how much of building companies, works the same way. We draw a box around what something is for and stop looking the moment it does its one job. Cancer rates are climbing in people under fifty, and the researchers behind this work are careful to say it's early. But a drug already sitting in tens of millions of medicine cabinets, with decades of safety data behind it, is about as low a barrier as science gets to explore an idea further. That alone makes it worth watching closely.
"The best ideas rarely look like what we expected going in.”
— Paul Gravette, CEO & Founder, Gravette Capital