Prometheus Biosciences stock became part of Merck in 2023

Prometheus Biosciences stock became part of Merck's portfolio in 2023 after the biotechnology company was acquired for USD 10.8 billion. The next chapter is now being written through Merck's inflammatory bowel disease pipeline, where a Prometheus-originated therapy delivered a Phase 3 trial result in September 2026.

Merck advances the IBD asset

On September 10, 2026, Pharmaphorum reported that Merck's tulisokibart helped patients with a type of inflammatory bowel disease achieve clinical remission in a pivotal Phase 3 trial. The drug originated at Prometheus under the name PRA023 before Merck acquired the company.

That result changes the way RXDX is analyzed. The former listing no longer represents a standalone biotechnology business, but its scientific output remains connected to a major commercial development program. For investors reviewing the old ticker, the relevant question is therefore the value transferred into Merck's pipeline rather than a live quotation for Prometheus shares.

The acquisition set a clear benchmark

According to Multiples VC, Merck agreed to buy Prometheus on April 16, 2023, for USD 200 per share, representing a 75 percent premium to the prior closing price. The transaction carried an equity value of approximately USD 10.8 billion.

The numerical comparison matters because it marks the last public-market valuation of the company. Prometheus was not merely absorbed as a research platform; the purchase price assigned a concrete value to its diagnostics, therapeutic candidates and IBD expertise. The September 2026 trial result provides a fresh operating milestone for an asset that was included in that valuation.

RXDX remains a historical ticker

Prometheus Biosciences carried the RXDX ticker on Nasdaq before the Merck transaction. The company operated in biotechnology and focused on inflammatory bowel disease, while its former public equity now belongs to the history of the acquisition.

For market readers, the distinction is essential. Prometheus Biosciences stock is a case study in how a public biotechnology investment can convert into exposure to a larger pharmaceutical pipeline, with the USD 200 per-share deal price and the 75 percent premium providing the final standalone benchmark.