Biologic DMARD — IL-23 Inhibitor (Anti-p19) Pregnancy: As a precautionary measure it is preferable to avoid use during pregnancy. There are limited data from use in pregnant women; animal studies do not indicate direct or indirect harmful effects with respect to pregnancy, embryonic/foetal development, parturition or postnatal development. Women of childbearing potential should use effective methods of contraception during treatment and for at least 12 weeks after treatment. It is unknown whether guselkumab is excreted in human milk; a risk to the breast-fed infant during the first few days after birth cannot be excluded.

Guselkumab

Brand names: Tremfya

Guselkumab is a subcutaneous interleukin-23 (IL-23) inhibitor monoclonal antibody used in moderate-to-severe plaque psoriasis and psoriatic arthritis.

Auto-extracted from the source labelling — not yet independently clinician-verified. These values were distilled from the UK SPC (or the US label where noted) but have not had a clinician sign-off. Confirm against the current SmPC before prescribing.

Adult dose

Dose: 100 mg (plaque psoriasis and psoriatic arthritis)

Route: Subcutaneous injection into the abdomen, thigh or back of the upper arm

Frequency: At weeks 0 and 4, followed by a maintenance dose every 8 weeks

Fetched UK SPC: Tremfya 100 mg OnePress solution for injection in pre-filled pen (eMC product 9587). Intended for use under the guidance and supervision of a physician experienced in the diagnosis and treatment of the conditions for which it is indicated. Plaque psoriasis: consideration should be given to discontinuing treatment in patients who have shown no response after 16 weeks. Psoriatic arthritis: same regimen; for patients at high risk for joint damage according to clinical judgement a dose of 100 mg every 4 weeks may be considered; consider discontinuing if no response after 24 weeks. Crohn's disease and ulcerative colitis (different presentations — refer to the separate SmPCs for Tremfya 200 mg concentrate for solution for infusion and Tremfya 200 mg solution for injection): induction is either 200 mg by intravenous infusion at weeks 0, 4 and 8, or 400 mg by subcutaneous injection (given as two consecutive 200 mg injections) at weeks 0, 4 and 8; the recommended maintenance dose starting at week 16 is 100 mg subcutaneously every 8 weeks, or alternatively, for patients without adequate therapeutic benefit from induction, 200 mg subcutaneously starting at week 12 and every 4 weeks thereafter; immunomodulators and/or corticosteroids may be continued, and corticosteroids may be reduced or discontinued in responders; consider discontinuing if no evidence of therapeutic benefit after 24 weeks. Missed dose: administer as soon as possible, then resume the regular schedule. No dose adjustment is required in the elderly, or in renal or hepatic impairment (not studied, but no significant impact on monoclonal antibody pharmacokinetics is expected). Do not inject into areas where the skin is tender, bruised, red, hard, thick or scaly, and if possible avoid areas of skin showing psoriasis. After proper training patients may self-inject if the physician determines this is appropriate. Paediatric (no per-kg dose is stated, so paedDose is null): the SPC states safety and efficacy in children and adolescents below the age of 18 years have not been established and no data are available. Verify any under-18 use against a children's formulary.

Dose adjustments

Renal

Not studied in renal impairment; renal impairment is generally not expected to have any significant impact on the pharmacokinetics of monoclonal antibodies and no dose adjustment is considered necessary.

Dose auto-extracted from UK Summary of Product Characteristics (SPC) via the eMC; US FDA prescribing information (openFDA / DailyMed) — cross-check; US labelling may differ from UK — not yet clinician-verified. Always confirm against the product SmPC and your local formulary before prescribing.

Contraindications

Serious hypersensitivity to the active substance or to any of the excipients
Clinically important active infections (e.g. active tuberculosis)

Side effects

Respiratory tract infections (very common — approximately 15% in the psoriasis and psoriatic arthritis studies)
Headache (common)
Diarrhoea (common)
Rash (common); urticaria (uncommon)
Arthralgia and injection site reactions (common)
Transaminases increased (common); neutrophil count decreased (uncommon); hypersensitivity and anaphylaxis (rare)

Interactions

CYP450 substrates — chronic inflammation can alter CYP450 enzyme formation; an exploratory study suggested a low potential for clinically relevant interactions with drugs metabolised by CYP3A4, CYP2C9, CYP2C19 and CYP1A2, but interaction potential cannot be ruled out for drugs metabolised by CYP2D6. On starting guselkumab in patients receiving concomitant CYP450 substrates, particularly those with a narrow therapeutic index, consider monitoring for therapeutic effect or drug concentration and consider dosage adjustment as needed (US labelling §7.1)

Clinical monograph

How it works

It is a human monoclonal antibody that binds the p19 subunit of IL-23, blocking IL-23-driven activation of the Th17 inflammatory pathway.

Prescribing in practice

It increases susceptibility to infection, so active serious infection should be treated and latent tuberculosis evaluated before starting.
It is initiated by specialists for patients meeting eligibility criteria for biologic therapy.
Live vaccines should be avoided during treatment, and hypersensitivity reactions can occur.

Monitoring

Assess for tuberculosis and infection before starting and review treatment response and infection risk during therapy.

Counselling the patient

Report signs of infection promptly and complete any pre-treatment screening.
Avoid live vaccines during treatment and update vaccinations beforehand where possible.
Follow the injection technique taught and store the device as directed.

Evidence & guidelines

Efficacy was demonstrated in the VOYAGE psoriasis and DISCOVER psoriatic arthritis randomised controlled trials.

Reference: NICE TA596; DISCOVER-1 Trial (Ann Rheum Dis 2020); DISCOVER-2 Trial (Lancet 2020); SPC Tremfya; Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. The structured dose values shown have been reviewed by a clinician. Monograph status: clinician-reviewed (2026-07-04).

Curated clinical cross-links plus same-class fallbacks.

Calculators

Drugs

Risankizumab (Rheumatology) · Biologic DMARD — IL-23 Inhibitor (Anti-p19)

Pathways