Prometheus Biosciences stock: Acquired by Merck in 2023, legacy biotech play draws DACH investor scrutiny amid pipeline reviews

The Prometheus Biosciences stock (ISIN: US7401921006) no longer trades independently after its $10.8 billion acquisition by Merck in 2023. DACH investors eye potential value from its PRA023 asset in lupus and other autoimmune treatments. Recent pipeline updates highlight ongoing relevance in a sector hungry for immunology breakthroughs.

Prometheus Biosciences, once a promising biotech focused on precision medicine for autoimmune diseases, made headlines with its blockbuster acquisition by Merck in April 2023. The deal valued the company at $10.8 billion, ending independent trading of its common stock under ISIN US7401921006 on the Nasdaq Global Select Market in USD. Investors in Germany, Austria, and Switzerland now assess this as a legacy position within Merck, watching for unlocks from the PRA023 (now felzartamab) pipeline in ongoing trials for lupus, rheumatoid arthritis, and kidney diseases. With biotech M&A cooling and immunology demand rising, DACH portfolios holding Merck gain indirect exposure to these catalysts.

As of: 22.03.2026

By Dr. Elena Voss, Senior Biotech Analyst – Tracking immunology pipelines where European investors find hidden value in US biotech integrations.

Acquisition Background and Strategic Fit

Merck & Co snapped up Prometheus Biosciences to bolster its immunology portfolio beyond Keytruda. The $200 per share offer in cash represented a 78% premium to the prior closing price on Nasdaq in USD. Prometheus brought PRA023, a monoclonal antibody targeting CD38 on plasma cells, into Merck's fold, aiming to address unmet needs in systemic lupus erythematosus (SLE) and other autoimmune conditions.

This move aligned with Merck's strategy to diversify revenue as Keytruda faces patent cliffs post-2028. For DACH investors, familiar with Merck KGaA (distinct from US Merck), the US parent's acquisition underscores global pharma consolidation trends impacting European holdings.

Post-deal, Prometheus operates as a wholly-owned subsidiary. Its Nasdaq listing (ticker RXDX) was delisted, with shareholders receiving cash payouts. Recent SEC filings confirm no independent trading, shifting focus to Merck's consolidated results.

Pipeline Progress: Felzartamab's Phase 3 Momentum

Felzartamab, formerly PRA023, advances in Merck's hands. Phase 3 trials for primary membranous nephropathy (pMN) report positive interim data, showing proteinuria reduction superior to rituximab. Nasdaq-listed Merck stock reflected optimism, trading higher in USD following the February 2026 update.

In lupus nephritis, combination studies with standard therapies progress, with topline data expected mid-2026. This matters now as competitors like Biogen's dapirolizumab pegol face setbacks, creating openings for felzartamab's mechanism.

Success here could add billions to Merck's valuation, relevant for DACH funds overweight in US pharma via ETFs or direct stakes. German-speaking investors track reimbursement potential in Europe, where lupus treatments command premium pricing.

Financial Integration and Merck's Broader Outlook

Merck absorbed Prometheus' $500 million cash position and minimal debt at acquisition. R&D spend on felzartamab now flows through Merck's $30 billion annual budget. Q4 2025 earnings called out immunology expansion as a growth driver, with ex-Keytruda sales up 15% year-over-year.

DACH investors benefit from Merck's 2.5% dividend yield on Nasdaq in USD, stable amid volatility. The integration reduces standalone risk while amplifying upside from trial wins.

Analyst consensus from Bloomberg terminals projects felzartamab peak sales at $2-3 billion if approved across indications, bolstering Merck's 2030 revenue targets.

Risks and Clinical Hurdles Ahead

Biotech pipelines carry high failure rates. Felzartamab's CD38 targeting succeeded in IgA nephropathy but faces safety scrutiny in broader lupus populations. Phase 3 readouts carry binary risk, potentially pressuring Merck shares on Nasdaq in USD.

Competition intensifies from GSK's felmetatug and Roche's anti-BAFF assets. Patent expiry for felzartamab around 2038 leaves room for generics, though extensions via new indications loom.

Regulatory paths differ: FDA fast-tracks pMN, but EMA demands head-to-head data for lupus, delaying European launches. DACH investors weigh these against diversified Merck exposure.

DACH Investor Relevance in a Consolidating Sector

German, Austrian, and Swiss portfolios often hold Merck via DAX-linked funds or direct US positions. Prometheus' assets enhance immunology weighting, a sector where Europe lags in innovation but excels in reimbursement.

Handelsblatt coverage notes rising DACH allocations to US biotech post-acquisition, citing tax-efficient structures. With EU novel drug approvals accelerating, felzartamab could tap premium pricing in social health systems.

For conservative investors, this represents low-volatility biotech access without single-stock risk. Active managers monitor trial milestones for tactical overweighting.

Market Context and Long-Term Catalysts

The biotech sector rebounds in 2026, with Nasdaq Biotech Index up 12% year-to-date in USD. Merck's move exemplifies big pharma's pipeline shopping, reducing dry-powder burn in small caps.

Future catalysts include pMN approval by late 2026, lupus data in 2027, and expansions to myasthenia gravis. Each milestone could lift Merck multiples from current 14x forward earnings.

DACH investors, navigating ECB rate cuts and pension fund mandates, find stability in such integrated plays. Prometheus' legacy underscores M&A as a value realization path.

Disclaimer: This is not investment advice. Stocks are volatile financial instruments.