Creating PROTACs and RIPTACs: Tim Shannon on The Long Run

Tim Shannon is today’s guest on The Long Run.

Tim is a general partner at Canaan Partners. He was a pulmonary and critical care physician in the early part of his career, before moving over to R&D leadership in industry, and then eventually into venture capital investing.

Tim Shannon, general partner, Canaan Partners

Tim got started as a VC during the Great Financial Crisis. That may not sound good, but it was the beginning of a biotech venture capital boom. During those years, Tim met Craig Crews, a professor of chemistry and pharmacology at Yale University. They got to work together on New Haven, Conn.-based Arvinas, a developer of a new class of small molecule drugs that act as targeted protein degraders, or PROTACs for those who like snappy acronyms.

They followed up that company by working together on Halda Therapeutics. It developed a different type of targeted protein degrader that acts through induced proximity, or a ‘hold and kill’ mechanism. These drugs are called RIPTACs for short. Halda was acquired a little over a year ago by Johnson & Johnson for $3 billion, based on encouraging early results for patients with advanced prostate cancer. Many other scientists are seeking to build on this success.

This conversation touches on an important concept that doesn’t get discussed often enough. Timing is important in biotech. You don’t want to be too early, or too late, when a new technology wave emerges.

The Long Run is sponsored by AlphaSense

So far 2026 has been a year of transition for healthcare and life sciences. Over the first half of this year, the AlphaSense healthcare research team analyzed the individual stories moving the needle across the life sciences ecosystem as part of the Sector Spotlight series. They feature the high-stakes battles for new drug markets (like oral GLP-1s and targeted radioligand therapies), a resurgent biotech IPO market, and more.

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Please enjoy this conversation with Tim Shannon on The Long Run.