JAK3 Inhibitors
5 drugsAbout JAK3
Janus kinase 3 (JAK3) is a protein kinase crucial for signaling in hematopoiesis and immune function. It modulates cytokine receptor signaling, impacting immune cell development and activity. As such, JAK3 is a key regulator of immune responses.
JAK3 is a validated drug target with strong genetic support (max score 0.93) linking loss-of-function variants to severe combined immunodeficiency. This genetic evidence, combined with clinical efficacy, supports JAK3 inhibition as a therapeutic strategy.
Five FDA-approved small molecule drugs target JAK3, including XELJANZ, XELJANZ XR, ANZUPGO, LITFULO and LEQSELVI. These drugs, developed by companies like Pfizer and Sun Pharma, are used in immunology and other therapeutic areas.
JAK3 Genetic Evidence Strong
Strong genetic evidence links JAK3 loss-of-function to severe combined immunodeficiency (score 0.93).
Strong genetic support suggests that targeting JAK3 has a higher probability of clinical success.
💡 Why activation?
- • Loss-of-function variants increase disease risk (OR > 1) — restoring function may help
- • 100% directional consistency across 3 traits
- • Strong signal in immune system disease, genetic, familial or congenital disease, phenotype pathways
Cross-Disease Effects
Trade-off: LowDirection of Effect
100% alignedEvidence Across Diseases
6 totalGWAS and other genetic studies link JAK3 to 6 diseases.
Loss-of-function causes disease; activation may help
Loss-of-function causes disease; activation may help
🔗 Colocalization Evidence 8 strong
max H4: 1.00eQTL/pQTL signals for JAK3 colocalize with these GWAS traits, providing causal evidence that gene expression changes drive disease risk.
Understanding these scores
Association Score (0-1): Combines all evidence types (genetic, literature, drugs, animal models). Higher = more evidence linking target to disease. This is a ranking heuristic, not a confidence score.
L2G Score: Open Targets uses a machine learning model (Locus-to-Gene) to predict which gene is causal at each GWAS locus. L2G=0.5 means ~50% probability of being the causal gene. Only associations with L2G > 0.05 are included.
Odds Ratio (OR): From gene burden studies (UK Biobank, AstraZeneca PheWAS). Measures how loss-of-function variants affect disease risk. OR<1 = protective (inhibiting target may help), OR>1 = risk (losing function causes disease).
Beta (β): Effect size for continuous traits. β<0 = protective, β>0 = risk.
Clinical Translation (~1.8x): Based on Nelson et al. 2015: drug targets with genetic evidence have ~2x higher success rates in clinical trials. We estimate: Strong support (score ≥0.7) → ~1.8x, Moderate (0.3-0.7) → ~1.3x, Weak → baseline.
Colocalization (H4): Tests whether a GWAS signal and an eQTL/pQTL signal share the same causal variant. H4 is the posterior probability that both traits are associated AND share a causal variant. H4 > 0.8 = strong evidence that gene expression/protein levels drive disease risk. This links genetic variation → gene expression → disease, supporting the target-disease connection.
Top JAK3 Drugs
Four companies, including Pfizer and Sun Pharma, have approved JAK3-targeting drugs.
The presence of multiple players indicates a competitive market with moderate entry barriers.
| Drug | Company | Approved | Indications |
|---|---|---|---|
| XELJANZ XR | Pfizer | 2016 | 5 |
| LITFULO | Pfizer | 2023 | 1 |
JAK3 Drug Modality Landscape
Modalities
Routes of Administration
JAK3 is amenable to small molecule drugs, with oral options available for convenient dosing.
The modality landscape suggests an opportunity to develop novel JAK3-targeting biologics.
JAK3 Clinical Trials 109 trials
Phase 1-4 trials started in 2008 or later that test an FDA-approved drug acting on JAK3. Source: ClinicalTrials.gov. How we count
Completion by Phase
| Phase | Total | Completed | Stopped | Active | Completion |
|---|---|---|---|---|---|
| Phase 1 | 28 | 24 | 1 | 3 | 96% |
| Phase 2 | 35 | 14 | 4 | 17 | 78% |
| Phase 3 | 28 | 18 | 1 | 9 | 95% |
| Phase 4 | 18 | 9 | 1 | 8 | 90% |
Top Sponsors
By Modality
Top Conditions
Phase 3 Readout Calendar Pro
1 Phase 3 trial testing approved JAK3 drugs across all sponsors.
Coverage: trials whose intervention is an approved drug targeting JAK3. Pre-approval candidates with development codes (e.g. AZD0901, MK-7240) are not yet linked. Anchored on CT.gov primary completion date.
JAK3 Drug Approval Timeline (2012 - 2025)
The first JAK3 inhibitor was approved in 2012, with the most recent approval in 2025.
The recent approval suggests continued interest and potential for further development in this area.
Pro Intelligence Preview
Deep insights for drug target analysis
Competitive Landscape
- • 3 companies competing
- • Market share by company
Full Drug Portfolio
- • All 5 approved drugs
- • Approval dates & indications
Genetic Validation
- • Full genetic evidence table
- • Effect sizes & directions
Approval Timeline
- • Full 5-drug timeline
- • First-of-modality markers
Clinical Trials Analysis
- • Sponsors: 62 (16 companies)
- • Completion rates by condition
Full summary • All drugs • Genetic evidence • Trials • Timeline
How We Count Trials
- Trials: phase 1-4 interventional trials on ClinicalTrials.gov that started in 2008 or later and test an FDA-approved drug acting on JAK3. A trial counts if an approved drug acting on JAK3 is in any arm, including as a comparator, and a trial that tests two such drugs counts once. Trials that test only unapproved drugs are not counted. A trial listed as phase 1/2 counts as phase 1, and phase 2/3 as phase 2.
- Active: recruiting, not yet recruiting, enrolling by invitation, or active and no longer recruiting.
- Completion rate: of the trials that have ended, the share marked Completed rather than Terminated or Withdrawn. Completed means the trial ended as planned; it does not mean the drug worked. Suspended trials are not counted as ended.
- Stopped: terminated or withdrawn. Trials stop for many reasons, including slow enrolment and business decisions, not only safety or efficacy.
- Sponsors: the lead sponsor of each trial. Companies are the sponsors ClinicalTrials.gov classes as industry; the rest are universities, hospitals, cooperative groups, government bodies and individuals.