Celldex's CDX-622 heads to Q3 data after early doses cut tryptase 50%
The Phase 1 trial has completed with 85 healthy volunteers; multiple-dose and subcutaneous data due by September will show whether the mast cell and TSLP signal holds beyond a single dose.
Executive Summary
- Celldex has completed enrollment in its Phase 1 trial of CDX-622 and is preparing to disclose data from the multiple-dose and subcutaneous portions, the pieces of the study still unreported.
- A single intravenous dose already showed durable pharmacodynamic activity and a clean tolerability profile, setting a specific bar the multiple-dose data need to reproduce rather than improve on.
- The mechanism combines two non-overlapping pathways in a single bispecific antibody, and no other program pairs mast cell depletion with TSLP neutralization, so this readout mainly informs Celldex's own next step rather than a competitive field.
- A repeat-dose and subcutaneous signal consistent with the single-dose result would clear the way for the Phase 1b proof-of-mechanism study in mild-to-moderate asthma the company has already outlined.
The catalyst
Celldex Therapeutics said it expects to report data from Part 2 (multiple ascending doses) and Part 3 (single ascending subcutaneous dose) of its Phase 1 trial of CDX-622 in the third quarter of 2026, a window running from July 1 through September 30. The trial, NCT06650761, completed on April 24, 2026, after enrolling 85 healthy volunteers in a randomized, double-blind, placebo-controlled dose-escalation design. The primary endpoint is safety, graded on the Toxicity Grading Scale for Healthy Adult and Adolescent Volunteers Enrolled in Preventive Vaccine Trials, with infusion reactions graded under CTCAE v5.0. Celldex+1Celldex Announces Initial Positive Results from Phase 1 Trial of CDX-622 Demonstrating ...Oct 30, 2025A Phase I Study of CDX-622NCT06650761
Probability of SuccessBased on the AppliedXL Probability of Success model. For more information about the methodology, read the research here.
What the single dose showed
Celldex disclosed initial results from the single-ascending-dose portion in October 2025: CDX-622 was well tolerated, with no dose-limiting toxicities, serious adverse events, or infusion reactions, and no signal of systemic KIT inhibition despite the drug's mechanism of starving stem cell factor signaling. A single 9 mg/kg dose produced a serum half-life of about 18 days with no detectable anti-drug antibodies, and doses across the range drove a sustained decrease of roughly 50% in circulating tryptase, a marker of mast cell activity, over a 12-week observation period. Tibor Keler, Celldex's chief scientific officer, said the company was "very pleased with the safety profile and the sustained dose dependent reductions in serum tryptase" and that the data supported moving into multiple-ascending-dose testing. That single-dose result is the benchmark the coming data must reproduce across repeat dosing and a subcutaneous route, not a bar it needs to beat. CelldexCelldex Announces Initial Positive Results from Phase 1 Trial of CDX-622 Demonstrating ...Oct 30, 2025
Trial mechanics
The trial's operational path was not a straight line. Its primary completion date moved from November 2025 to January 2026 and then to April 2026, three separate revisions logged in the registry between April 2025 and September 2025. Enrollment grew from 56 to 80 and then to 85 participants over the same period, growth consistent with a Phase 1 dose-escalation design adding cohorts rather than a target cut. The trial moved to Active, not recruiting in February 2026 and to Completed in May 2026, tracking the sponsor's own guidance that multiple-ascending-dose data would follow the single-dose readout. NCT06650761A Phase I Study of CDX-622NCT06650761
The competitive frame
No trial in the competitive field shares CDX-622's target combination of TSLP and stem cell factor, and Celldex's own materials describe the single-dose data as the first study of a stem cell factor-neutralizing antibody in humans. The nearest comparators in the broader healthy-volunteer trial population, including a corticosteroid study and an HIV capsid inhibitor program, work through unrelated mechanisms and indications, leaving CDX-622 without a direct precedent to benchmark against. That isolation means this readout's main readthrough is internal: whether the multiple-dose and subcutaneous data support Celldex's plan to move into a Phase 1b proof-of-mechanism study in patients with mild-to-moderate asthma, the step the company has already announced. CelldexCelldex Announces Initial Positive Results from Phase 1 Trial of CDX-622 Demonstrating ...Oct 30, 2025
This analysis was produced using AI-assisted reporting systems, AppliedXL data, and official public records. These systems undergo editorial review, quality checks, and regular audits by human experts. Errors may still occur, as with any automated system. Always consult the linked primary sources. Read our AI Editorial Policy.