HotSpot Therapeutics doesn't aim at the front door of a protein. It hunts the back rooms - the allosteric "hotspots" nature uses to switch proteins on and off - and builds small molecules to flip them.
Caption: A wordmark that looks calm. The chemistry behind it is anything but. - shot in the lobby at 50 Milk Street, Boston.
Walk into 50 Milk Street and you will not find anyone talking about a moonshot. You will find chemists arguing about pockets - specifically, the ones on proteins that most of the industry pretended did not exist.
HotSpot Therapeutics spent its first years as a platform company with a thesis. It is now something harder to dismiss: a clinical-stage company whose lead candidate, HST-1011, is being dosed in people with advanced cancer. The thesis grew teeth.
The numbers are tidy for a company this young. Three funding rounds. Roughly $210 million raised. About 61 employees. Four programs spanning cancer and autoimmune disease, all pointed at the same unusual idea.
The idea: most drugs jam a protein's active site, like gluing a lock shut. HotSpot would rather find the dimmer switch on the wall - the regulatory site evolution already built for the job.
"Pioneering a new approach to allosteric drug discovery by unlocking the on/off switches on proteins."- HotSpot Therapeutics
There is a polite word the pharmaceutical industry uses for proteins it cannot control: undruggable. It is a confession dressed as a category.
For decades, drug hunters crowded around the same well-behaved targets - enzymes with deep, obvious active sites a molecule could plug. Everything else, the flat surfaces and the proteins with no convenient pocket, got shelved. CBL-B. IRF5. The signalosomes behind KRAS-driven cancers. Important biology, no obvious handle.
The frustrating part is that nature controls all of these proteins constantly. Cells switch them on and off every second using allosteric sites - regulatory pockets away from the active site. The control panel was always there. The industry just was not looking at it systematically.
The targets were not undruggable. They were unaddressed - which is a much more embarrassing problem to admit.- The HotSpot thesis, paraphrased
Allosteric drugs were not new in 2017. They were lucky. The good ones tended to be found by accident, which is a difficult thing to put on a roadmap.
Jonathan Montagu and Geraldine Harriman, both from the allostery-focused biotech Nimbus Therapeutics, made a different wager. They bet that these regulatory hotspots were not random - that they shared features, that you could hunt them systematically, and that a platform could turn serendipity into a process.
Montagu took the CEO seat. Harriman became chief scientific officer. The early backers - Atlas Venture, Sofinnova Partners, SR One - put in $45 million to find out if the bet held.
They called the targets "natural hotspots" and treated allosteric pockets as undervalued real estate: prime biological property the rest of the market had walked past.
"HotSpot targets natural hotspots - a unique family of allosteric sites used by nature to regulate protein function."- Company description
The engine has two names worth knowing. SpotFinder finds the regulatory hotspots. Smart Allostery turns them into molecules - blending computation, AI, structural biology and medicinal chemistry into one assembly line.
What comes off that line is a pipeline of first-in-class small molecules, each aimed at a target other companies left on the shelf.
An oral small-molecule CBL-B inhibitor designed to take the brakes off the immune system in solid tumors resistant to anti-PD(L)1 therapy.
Phase 1/2Described as the first potent, selective small-molecule IRF5 inhibitors - aimed at lupus, Sjogren's, RA, systemic sclerosis and myositis.
IND-enablingAn IND-stage oncology program pointed at the signalosome behind KRAS G12X-driven solid tumors - a notoriously stubborn corner of cancer.
IND-enablingFind the switch nature already built. Then build the molecule that flips it. Everything else is detail.- How the platform works, abbreviated
A platform thesis is cheap. Investors writing larger checks each round is the closest thing biotech has to a verdict. HotSpot's rounds did not just repeat - they grew.
// Capital raised by round. The Series C was oversubscribed - a polite biotech way of saying more investors wanted in than there was room for.
Phase 1 data showed HST-1011 increasing immune activation in both blood and tumor tissue. The switch, it turns out, switches.- ESMO Congress 2024
The backer list reads like a who's-who of life-science capital: Atlas Venture and Sofinnova from the start, then Pivotal bioVenture Partners, LSP, B Capital Group, SR One and a roster of crossover funds joining for the Series C. EQT later listed the company among its portfolio. The conviction was not lonely.
The mission is narrow on purpose. HotSpot is not trying to drug everything. It is trying to drug the proteins that matter most in cancer and autoimmune disease - the ones with real biology and no good handle.
Cancer needs the immune system unleashed; that is the CBL-B story. Autoimmune disease needs it calmed down; that is the IRF5 story. Same platform, opposite directions, one underlying tool: control the switch.
Cancer wants the immune system louder. Autoimmunity wants it quieter. HotSpot sells the volume knob to both.- On serving two opposite markets
Here is the quiet stakes of all this. If HotSpot is right - if regulatory hotspots can be hunted on a schedule instead of stumbled upon - then a large slice of the proteome stops being off-limits.
That is the difference between a clever company and a foundational one. A clever company makes one good allosteric drug. A foundational one makes allostery a category you can plan around. The early clinical data does not settle it yet. But it is the first evidence that the assembly line produces molecules that do, in patients, what the platform predicted on a screen.
Back in the lobby at 50 Milk Street, the wordmark still looks calm. But the proteins it stands for - the ones the industry filed under undruggable - are now sitting in clinical trials, getting their switches flipped. The category did not change. The company did.
Undruggable was never a fact about proteins. It was a fact about who was willing to look. HotSpot looked.- The closing argument
Caption: Eight years, three rounds, and a list of proteins nobody else would touch. The lobby is quiet. The pipeline is not.