Is Tremfya an Immunosuppressant?
Yes, Tremfya (guselkumab) is an immunosuppressant—it is a monoclonal antibody that selectively blocks interleukin-23 (IL-23), thereby modulating the immune system and suppressing inflammatory pathways involved in autoimmune diseases.
Mechanism of Immunosuppression
Guselkumab is a human IgG1λ monoclonal antibody that specifically binds to the p19 subunit of IL-23, preventing IL-23 from interacting with its receptor 1. This blocks the IL-23/IL-17 inflammatory axis, which plays a central role in psoriasis, psoriatic arthritis, and ulcerative colitis pathogenesis 2, 3. By inhibiting IL-23, guselkumab:
- Reduces release of proinflammatory cytokines and chemokines 1
- Decreases Th17 cell activity and IL-17A, IL-17F, and IL-22 production 1
- Alters regulatory T cell and resident memory T cell populations 4
This targeted immunosuppression differs from broad immunosuppressants like methotrexate or TNF inhibitors, but it still fundamentally suppresses immune function.
Clinical Evidence of Immunosuppressive Effects
The 2019 AAD-NPF guidelines explicitly acknowledge the immunosuppressive nature of IL-23 inhibitors like guselkumab 5:
- Increased infection risk: Phase III studies indicate an increased risk of infection with guselkumab 5
- Combination therapy concerns: Combining IL-23 inhibitors with methotrexate can further increase infection risk 5
- Monitoring requirements: Guidelines recommend screening for latent tuberculosis, hepatitis B and C, and HIV before treatment—standard practice for immunosuppressants 5
Practical Implications for Clinical Use
Pre-Treatment Screening (Required for Immunosuppressants)
- TB testing (PPD or Quantiferon Gold) 5
- Hepatitis B and C serology 5
- Complete blood count and metabolic profile 5
- HIV testing based on risk factors 5
Contraindications and Precautions
- Absolute contraindication: History of allergic reaction to guselkumab 5
- Temporary discontinuation: Hold during febrile illness or active infections requiring antibiotics; restart only after complete resolution 5
- Use caution: In patients with pre-existing immunosuppression-related conditions 5
Ongoing Monitoring
- Periodic screening for infections 5
- Annual TB testing in high-risk patients 5
- Evaluation for nonmelanoma skin cancer 5
Safety Profile
While guselkumab is generally well-tolerated 6, 7, its immunosuppressive effects manifest as:
- Increased susceptibility to infections (particularly mucocutaneous candidiasis with IL-17 inhibitors, though less common with IL-23 inhibitors) 5
- Rare cases of elevated liver transaminases 5
- No unique adverse events compared to other biologics, but the immunosuppressive mechanism remains 5
Common Pitfall to Avoid
Do not assume that "targeted" or "selective" immunosuppression means "not immunosuppressive." Guselkumab's selectivity for IL-23p19 makes it more targeted than older agents, but it still suppresses critical immune pathways. Treat it as an immunosuppressant in all clinical decision-making, including infection screening, vaccination timing, and perioperative management.
The FDA label explicitly states guselkumab is "an interleukin-23 antagonist" that "inhibits the release of proinflammatory cytokines" 1—this is immunosuppression by definition, even if more selective than traditional agents.