How does ciclosporin suppress the immune system?

It binds cyclophilin and inhibits calcineurin, which blocks interleukin-2 production and prevents T-cell activation.

Why does ciclosporin require blood-level monitoring?

It has a narrow therapeutic index and variable absorption, so whole-blood trough or C2 levels are measured to keep exposure effective but not toxic.

What are the main side effects of ciclosporin?

Dose-dependent kidney injury, high blood pressure, gum overgrowth, excess hair growth and tremor are common, alongside the class-wide infection and cancer risks of immunosuppression.

Is ciclosporin a peptide?

Yes. It is a cyclic undecapeptide (an 11-amino-acid ring) of fungal origin, which is why it appears in a peptide reference.

EMA-approvedaka Cyclosporine A, Sandimmune, Neoral

Ciclosporin — Complete Research Guide (2026)

Last updated 2026-06-30

TL;DR

Ciclosporin (also known as Cyclosporine A) is a peptide catalogued under Cyclic & Antimicrobial (Immunosuppressant). It is described as: Cyclophilin/calcineurin. Documented context: Transplant rejection; autoimmune. Neutral reference entry; EU status: EU-approved prescription medicine.

What is Ciclosporin?

Ciclosporin (cyclosporine, cyclosporin A) is a cyclic undecapeptide isolated from the fungus Tolypocladium inflatum and one of the first calcineurin inhibitors.

It is approved by the FDA and EMA to prevent rejection of kidney, liver and heart allografts and to treat certain autoimmune diseases such as severe psoriasis and rheumatoid arthritis.

Its use is supported by multiple randomized controlled trials and more than four decades of clinical experience.

How does Ciclosporin work?

Ciclosporin binds the intracellular protein cyclophilin, and this complex inhibits the phosphatase calcineurin.

Blocking calcineurin prevents dephosphorylation of NFAT and suppresses transcription of interleukin-2 and other cytokines required for T-cell activation.

What does the research say about Ciclosporin?

In a randomized controlled trial, ciclosporin improved one-year cadaveric kidney graft survival compared with conventional azathioprine-plus-steroid immunosuppression. ^[2]
The graft-survival advantage of ciclosporin over conventional therapy was maintained at three years of follow-up. ^[3]
An early human series showed ciclosporin used as the sole initial immunosuppressant could sustain cadaveric kidney, pancreas and liver grafts, establishing its transplant role. ^[1]

Clinical research & studies

The references below are the primary sources cited throughout this guide. Each links directly to PubMed or the regulator. Where evidence is preclinical (animal or in-vitro), that is stated rather than implied.

[1] Cyclosporin A initially as the only immunosuppressant in 34 recipients of cadaveric organs: 32 kidneys, 2 pancreases, and 2 livers — Calne RY et al., Lancet 1979. (Human case series)
[2] A randomized clinical trial of cyclosporine in cadaveric renal transplantation — Canadian Multicentre Transplant Study Group, The New England Journal of Medicine 1983. (Randomized controlled trial)
[3] A randomized clinical trial of cyclosporine in cadaveric renal transplantation. Analysis at three years — Canadian Multicentre Transplant Study Group, The New England Journal of Medicine 1986. (Randomized controlled trial, extended follow-up)
[4] Calcineurin inhibitor nephrotoxicity — Naesens M et al., Clinical Journal of the American Society of Nephrology 2009. (Review)
[5] Cyclosporin A in cadaveric organ transplantation — Calne RY et al., British Medical Journal 1981. (Human clinical study)

Dosing context

This is not medical advice or a usage recommendation. Dosing figures are reported research context only, cited from the published literature.

This is context only and not dosing guidance: ciclosporin dosing is individualized by transplant type, co-medication and body weight, and is adjusted to target whole-blood drug concentrations.

Because absorption is variable and toxicity is concentration-related, therapeutic drug monitoring using trough (C0) or 2-hour (C2) levels is standard practice.

Side effects & safety profile

As with all immunosuppressants, ciclosporin increases the risk of serious infections and of malignancy, including lymphoma and skin cancers, reflecting the class boxed-warning risk.

Drug-specific, dose-dependent adverse effects include nephrotoxicity, hypertension, gingival hyperplasia, hirsutism and tremor.

Its narrow therapeutic index requires whole-blood level monitoring to balance efficacy against toxicity.

Stacking & combinations

In transplantation ciclosporin is typically combined with corticosteroids and an antimetabolite (azathioprine or mycophenolate) as part of a multi-drug maintenance regimen.

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Frequently asked questions

It is approved to prevent rejection of kidney, liver and heart transplants and to treat certain autoimmune conditions such as severe psoriasis and rheumatoid arthritis.

References

[1] Cyclosporin A initially as the only immunosuppressant in 34 recipients of cadaveric organs: 32 kidneys, 2 pancreases, and 2 livers — Calne RY et al., Lancet 1979. PMID: 91781. View sourceStudy: Human case seriesCiclosporin used alone could sustain cadaveric organ grafts in humans, launching its clinical development.
[2] A randomized clinical trial of cyclosporine in cadaveric renal transplantation — Canadian Multicentre Transplant Study Group, The New England Journal of Medicine 1983. PMID: 6350878. View sourceStudy: Randomized controlled trialCiclosporin improved one-year renal allograft survival versus conventional azathioprine-steroid therapy.
[3] A randomized clinical trial of cyclosporine in cadaveric renal transplantation. Analysis at three years — Canadian Multicentre Transplant Study Group, The New England Journal of Medicine 1986. PMID: 2871486. View sourceStudy: Randomized controlled trial, extended follow-upThe graft-survival benefit of ciclosporin persisted at three years.
[4] Calcineurin inhibitor nephrotoxicity — Naesens M et al., Clinical Journal of the American Society of Nephrology 2009. PMID: 19218475. View sourceStudy: ReviewReviews the acute and chronic nephrotoxicity that limits long-term calcineurin-inhibitor use.
[5] Cyclosporin A in cadaveric organ transplantation — Calne RY et al., British Medical Journal 1981. PMID: 6781658. View sourceStudy: Human clinical studyConfirmed ciclosporin's immunosuppressive efficacy while flagging nephrotoxicity in cadaveric organ recipients.

This article is for educational and research purposes only. Peptides discussed here are not approved for human consumption by the FDA, EMA, or equivalent regulators outside of specific clinical contexts. Always consult a licensed medical professional before any therapeutic use.