CPTX2309 by AbbVie: status and timeline

CPTX2309

In vivo CAR-T that delivers anti-CD19 mRNA to CD8+ T cells. Depletes B cells without chemotherapy or ex vivo manufacturing.

PilotStage 3 of 5

Phase 1 underway in healthy volunteers since June 2025 with B cell depletion kinetics being evaluated.

Updated 30 Jun 2025Checked 10 Oct0 updates this week

Milestones

Next · Phase 1 final data readout

Capstan acquired by AbbVie for $2.1B30 Jun 2025Complete.
First participants dosed in Phase 1 trialJun 2025Complete.
Phase 1 safety and B cell depletion data evaluationQ4 2025Complete.
Phase 1 final data readoutTarget Q4 2026Not yet reached.

Most important updates

Upcoming

Q4 2026Phase 1 final data readout (next)

Current obstacles

Achieving deep and durable B cell depletionPreclinical data shows profound depletion, but Phase 1 must confirm this translates to humans and achieves the clinical efficacy needed for autoimmune reset.
Balancing CAR durability and safetyThe CAR must persist long enough to clear B cells but disappear before it causes immune suppression side effects. The optimal timing remains to be determined.

Physics limits

mRNA degradation limits persistencemRNA is naturally degraded by cellular machinery. The CAR effect is inherently transient, limiting the duration of B cell depletion unless multiple doses are used.
T cell exhaustion with repeated dosingCD8+ T cells may become exhausted if dosed repeatedly to maintain CAR expression, reducing their ability to kill target cells and mounting immune responses.

How it works

4 parts

LNP delivery

Targeted lipid nanoparticles

Lipid nanoparticles carrying anti-CD19 CAR mRNA are engineered to preferentially deliver the genetic cargo to CD8+ T cells in circulation.

CAR expression

Transient CAR-T engineering

CD8+ T cells express the CAR protein, gain ability to kill CD19+ B cells. CAR and mRNA degrade naturally over time.

B cell killing

Anti-CD19 recognition

CAR-expressing T cells recognize CD19 and kill B cells, depleting memory and naïve populations in blood and lymphoid tissues.

B cell recovery

Immune system reset

After CAR-T disappears, B cell precursors regenerate from bone marrow stem cells, restoring immune tolerance by repopulating with fresh, naïve B cells.

Spec sheet

Spec	CPTX2309
Preclinical B cell depletion	Rapid and profound in blood and tissues^R (reported)
Lymphodepletion required	No (versus ex vivo CAR-T)^R (reported)
Ex vivo cell manufacturing	Not required^R (reported)

^R reported by the company

Update log

2 updates

Mon 30 Jun 2025

Major: AbbVie acquires Capstan Therapeutics for $2.1 billion, gaining in vivo CAR-T platform CPTX2309 for autoimmune diseasesPressCommercial

Jun 2025

Major: Capstan Therapeutics begins Phase 1 trial of CPTX2309 in healthy volunteers; first participants dosedPressTest

About AbbVie

The team behind CPTX2309

AbbVie

Immunology, CAR-T, cell therapy, Botox, Humira

Global biopharma spun from Abbott in 2013. Blockbusters in Humira (rheumatology) and Botox. Acquired Capstan in 2025 for CPTX2309, an in vivo CAR-T.

AbbVie generates $61 billion annual revenue and is known for Humira and Botox.
Chairman and CEO Robert Michael has led the company since July 2024, with board promotion in March 2026.
Capstan acquisition in June 2025 brought CPTX2309, an in vivo CAR-T therapy in Phase 1 trials for B cell-mediated autoimmune diseases.

abbvie.com (opens abbvie.com)Company profile →

Founded: 201313 yrs
Headquarters: United States
Status: Public
Listed: ABBV (opens google.com)NYSE
Valuation: $465Bmarket capSep 2026
Staff: ~57,000Jan 2026
Works in: BiotechCell & organ therapies
Coverage: 1 program · 2 updateslatest 30 Jun 2025checked 10 Oct
Acquired by: Capstan Therapeutics (opens abbvie.com)
People: Robert Michael (opens abbvie.com)Chairman and Chief Executive Officer

Spec

CPTX2309

Preclinical B cell depletion

Rapid and profound in blood and tissues^R (reported)

Lymphodepletion required

No (versus ex vivo CAR-T)^R (reported)

Ex vivo cell manufacturing

Not required^R (reported)