$1.4 Billion Deal: Novartis Buys Tourmaline Bio and Its Phase 3-Ready IL-6 Antibody Pacibekitug

Updated: September 11, 2025

September 9, 2025 — Novartis announced it will acquire Tourmaline Bio (NASDAQ: TRML) for USD 48 per share in cash, valuing the company at approximately USD 1.4 billion. Following a tender offer and merger, Tourmaline will become a wholly owned Novartis subsidiary. The transaction is expected to close in the fourth quarter of 2025. This report explores pacibekitug’s complex development history, its repositioning as an anti-inflammatory cardiovascular therapy, and the strategic rationale behind Novartis’ acquisition amid an evolving competitive landscape.

Pacibekitug: An Inflammation-Targeted Therapy

Tourmaline’s lead asset, pacibekitug, is a fully human anti-IL-6 IgG2 monoclonal antibody designed to suppress systemic inflammation — a key driver of atherosclerotic cardiovascular disease (ASCVD).

Originally developed at Pfizer as PF-04236921, pacibekitug was discovered using the UltiMAb® transgenic mouse platform from Medarex — a technology responsible for multiple FDA-approved monoclonal antibodies. Pfizer engineered the molecule as an IgG2 isotype to reduce Fc receptor binding and immune activation, aligning it with anti-inflammatory applications.

Pacibekitug has demonstrated a low incidence of anti-drug antibodies (0–1%) and can be delivered via subcutaneous injection as infrequently as once every 90 days (Q90D). By comparison, other IL-6 antibodies such as ziltivekimab and clazakizumab require monthly dosing and show higher immunogenicity rates (6–13% and up to 10%, respectively

Development History and Strategic Evolution

Following six early-phase clinical trials in autoimmune diseases between 2010 and 2016, Pfizer deprioritized the asset amid evolving pipeline priorities and competitive pressures. In 2022, Tourmaline Bio licensed the antibody, renamed it pacibekitug (TOUR006), and strategically repositioned it for ASCVD and other inflammation-driven diseases. Given its UltiMAb origin, industry observers note potential pass-through royalties to Bristol-Myers Squibb, which acquired Medarex in 2009, though no terms have been publicly disclosed. This journey reflects the molecule’s scientific robustness and the evolving strategic landscape in inflammation-targeted therapy.

Phase 2 TRANQUILITY trial: In patients with elevated hs-CRP, pacibekitug achieved a median hs-CRP reduction of ~85% at Day 90 with 15 mg monthly dosing (Q4W) and ~86% with 50 mg quarterly dosing (Q12W).
Safety profile: Overall rates of adverse events and serious adverse events were comparable to placebo.
Next step: Pacibekitug is now Phase 3–ready, with pivotal development in ASCVD expected under Novartis.

Strategic Rationale

Novartis has steadily expanded its cardiovascular pipeline, complementing its established Entresto® franchise with newer assets such as inclisiran (PCSK9 siRNA) and pelacarsen (Lp(a) antisense). Pacibekitug adds a new mechanism that addresses residual inflammatory risk, an area with high unmet need and no widely adopted therapies.

Novartis executives highlighted inflammation as a “major driver” of cardiovascular disease and emphasized pacibekitug’s differentiated mechanism and quarterly dosing as potential advantages in ASCVD care.

The quarterly dosing option could give pacibekitug a meaningful compliance and convenience advantage, particularly for long-term prevention in high-risk ASCVD patients.

Competitive Landscape

The cardiovascular anti-inflammatory race is heating up:

• Regeneron/Sanofi and Kiniksa are advancing IL-1 and IL-6 pathway inhibitors.
• Amgen is leading in Lp(a)-lowering with olpasiran.
• Ziltivekimab (Novo Nordisk, via Kiniksa): a fully human IgG1κ antibody with YTE mutation, monthly dosing (Q4W), immunogenicity rates 6–13%. Currently in the Phase 3 RESCUE trial for ASCVD.
• Clazakizumab (CSL): humanized rabbit IgG1κ antibody, tested in transplant and autoimmune settings. Monthly IV dosing (Q4W), immunogenicity up to 10%.
• Pacibekitug (Novartis/Tourmaline): fully human IgG2, low ADA incidence (0–1%), tested with quarterly SC dosing (Q12W).

Pacibekitug could stand out with its upstream IL-6 blockade and practical dosing schedule. However, its ultimate success will depend on showing event reduction in large cardiovascular outcomes trials, beyond the current biomarker data.

Outlook

The $1.4 billion deal underscores Novartis’ commitment to building leadership in cardiovascular medicine. Pacibekitug offers a bold bet on IL-6 inhibition as a new therapeutic pillar in ASCVD. Pivotal outcomes trials will be decisive in determining whether biomarker promise translates into reduced rates of myocardial infarction, stroke, and cardiovascular mortality.

Sources

• Novartis. Novartis to acquire Tourmaline Bio, complementing cardiovascular pipeline with pacibekitug for the treatment of atherosclerotic cardiovascular disease (ASCVD). Sep 9, 2025.
• Tourmaline Bio. IR news releases: Tourmaline Bio Enters into Agreement to be Acquired by Novartis AG and topline TRANQUILITY reporting. Sep 9, 2025.
• Pfizer Inc. Pfizer and Medarex Announce 10-Year Antibody Discovery Collaboration. Business Wire, Nov 15, 2004. https://www.businesswire.com/news/home/20041115005505/en/Pfizer-Medarex-Announce-10-Year-Antibody-Discovery-Collaboration
• Bristol-Myers Squibb Company. Bristol-Myers Squibb Completes Acquisition of Medarex, Inc. Press Release, Dec 1, 2009. https://news.bms.com/press-release/company-news/bristol-myers-squibb-completes-acquisition-medarex-inc
• Tourmaline Bio. Tourmaline Bio Enters Agreement to be Acquired by Novartis AG, and Reports Topline TRANQUILITY Results for Pacibekitug (TOUR006). Investor Relations, Sep 9, 2025. https://ir.tourmalinebio.com/news-releases/news-release-details/tourmaline-bio-enters-agreement-be-acquired-novartis-ag-and
• Synapse Medical Communications. Clinical Trials and Development History of PF-04236921 (Pacibekitug). Synapse Reports, 2023. https://www.synapsemedical.com/clinical_trials/pf-04236921
• Ridker PM, et al. Antiinflammatory Therapy with Canakinumab for Atherosclerotic Disease. N Engl J Med. 2017;377:1119–1131. (CANTOS trial).
• Ridker PM, et al. Effect of interleukin-6 inhibition with ziltivekimab on biomarkers of inflammation and cardiovascular disease: a randomized trial. Lancet. 2021;398(10305):117–126.
• Pergola PE, et al. Ziltivekimab, a novel IL-6 ligand monoclonal antibody, in patients with CKD and elevated hsCRP: a randomized phase 2 trial. J Am Soc Nephrol. 2021;32(7):1615–1626.
• Wada T, et al. Interleukin-6 inhibition and cardiovascular outcomes: insights from clinical studies. J Cardiol. 2023;81(1):46–53.
• Weinblatt ME, et al. Clazakizumab, an anti–interleukin-6 monoclonal antibody, for rheumatoid arthritis: results from a randomized, double-blind, placebo-controlled, dose-ranging trial. Arthritis Rheum. 2015;67(2):330–338.

Disclaimer: This article is for informational purposes only and does not constitute medical or investment advice. Readers should consult primary literature and official regulatory sources for verification.