S&P/ASX 200 Index (ASX: XJO) healthcare stock Telix Pharmaceuticals Ltd (ASX: TLX) is slipping today.

Shares in the diagnostic and therapeutic product developer closed on Friday trading for $23.99. In morning trade on Monday, shares are changing hands for $23.76 apiece, down 0.96%.

For some context, the ASX 200 is down 1.18% at this same time.

But don't feel too bad for longer-term shareholders.

As you can see on the chart above, it's been a banner year for Telix shareholders, with the ASX 200 healthcare stock still up more than 120% over 12 months.

Here's what's happening today.

ASX 200 healthcare stock expands US footprint

This morning, the ASX 200 healthcare stock announced it has entered into an asset purchase agreement with antibody engineering company ImaginAb. A concurrent technology license agreement will be signed at closing.

The purchase price for the transaction was reported to be US$45 million (AU$73 million). That's comprised of US$10 million in cash and US$31 million in equity at closing, along with a deferred payment of up to US$4 million in equity at the end of a 15-month indemnity period.

Telix said it will acquire a pipeline of next-generation therapeutic candidates, a proprietary novel biologics technology platform, and a protein engineering and discovery research facility from ImaginAb to enhance its existing innovation capabilities.

The company noted this adds to its pipeline of early-stage drug candidates against high-value targets, as well as several other novel targets in discovery stage.

The transaction also includes a staffed, state-of-the-art research facility in the US state of California, providing Telix with further in-house capabilities in antibody engineering and preclinical development.

Upon achievement of specific key development and commercial milestones, the ASX 200 healthcare stock will pay up to a total of US$185 million (AU$299 million), some of which could be paid in cash or equity at Telix's discretion.

Telix will issue shares to ImaginAb as consideration for the acquisition.

What did management say?

Commenting on the strategic transaction for the ASX 200 healthcare stock, Telix Therapeutics CEO Richard Valeix said:

The combination of a proprietary drug discovery platform, pipeline of promising theranostic assets and a talented team of subject matter experts will enhance Telix's research and innovation capability now and into the future.

This acquisition will enable Telix to explore new disease areas with state-of-the-art radiotherapeutic technology.

Anna M Wu, co-founder ImaginAb, added:

As the radiopharmaceutical sector gains momentum there is a significant need for targeting agents to be more selective, deliver less off-target radiation, and better match the pharmacology and radiobiology of a given radionuclide.

The team's deep expertise in antibody engineering and the resulting development of a valuable, proprietary platform technology has led to clinical proof-of-concept.

Completion of the transaction remains subject to customary conditions, including regulatory approvals and other third-party consents.