FDA-approved
Immune & defense
Cyclosporine
Also called ciclosporin
Cyclosporine is a cyclic peptide that suppresses T cells. Learn how it works, its FDA-approved forms, and why systemic versions carry boxed warnings.
- Reviewed by
- William Maish, MD MBA MPH, Clinical Product Lead
- Published
- October 5, 2026
- Last updated
- October 5, 2026
Key takeaway
Cyclosporine (also spelled ciclosporin; brands include Sandimmune, Neoral, and the eye drop Restasis) is a cyclic peptide from a fungus that suppresses the immune system, and it transformed organ transplantation when it arrived in the 1980s. It works by blocking the activation of T cells. It has been FDA-approved in the U.S. since 1983, is available in oral, intravenous, and eye-drop forms, and carries boxed warnings for the systemic versions.
At a glance
| What it is | A calcineurin-inhibitor immunosuppressant, a cyclic 11-amino-acid peptide of fungal origin |
| Approved for | Prevention of transplant rejection, severe rheumatoid arthritis, severe psoriasis, and (as Restasis) chronic dry eye |
| Key fact | In a landmark transplant trial it substantially improved one-year kidney graft survival over the prior standard |
| Route | Oral, intravenous, or ophthalmic |
| Evidence strength | FDA approved |
What is cyclosporine?
Cyclosporine, also spelled ciclosporin and known as cyclosporin A, is an immunosuppressant drug derived from a soil fungus. Chemically it is an unusual cyclic peptide, a ring of 11 amino acids including some that do not appear in ordinary proteins, which makes it fat-soluble and distinct from typical linear peptides. It is sold as Sandimmune, the microemulsion Neoral, and Gengraf for systemic use, and as the Restasis emulsion for the eyes. It was approved in the United States in 1983.
The history of cyclosporine
Cyclosporine changed the course of modern medicine. It was isolated from a fungus in the 1970s and found to suppress the immune system in a highly selective way, acting on the T cells that drive transplant rejection without broadly wiping out the bone marrow. Its approval in 1983 dramatically improved the survival of transplanted organs and helped make heart, liver, and other transplants routine rather than experimental. It remains a reference point for the calcineurin-inhibitor class.
How does cyclosporine work?
Cyclosporine enters T cells and binds a protein called cyclophilin, and the resulting complex blocks an enzyme called calcineurin. Calcineurin normally activates a transcription factor (NFAT) that switches on the gene for interleukin-2 and other signals T cells need to multiply and mount an immune response. By inhibiting calcineurin, cyclosporine prevents that activation, so the immune attack on a transplanted organ, or the overactive immune response in autoimmune disease, is suppressed.
That targeted suppression of T-cell activation is what made it so valuable in transplantation. In the landmark Canadian multicenter trial, cyclosporine improved one-year kidney graft survival1 compared with the older azathioprine-based regimen. The same mechanism underlies its use in autoimmune conditions and, at low local doses in Restasis, in reducing the inflammation of chronic dry eye.
Is it FDA-approved?
Yes. The FDA approved cyclosporine and two later formulations on this timeline:
| Year | FDA approval |
| 1983 | Cyclosporine, for transplant rejection |
| 1995 | Neoral microemulsion |
| 2002 | Restasis eye drop |
The systemic formulations carry boxed warnings, including for kidney toxicity and for the increased risk of serious infections and malignancies (especially lymphoma and skin cancer) that comes with immunosuppression.
What is cyclosporine prescribed for?
Systemic cyclosporine is prescribed to prevent rejection in kidney, liver, and heart transplants, and for severe rheumatoid arthritis and severe plaque psoriasis that have not responded to other treatment. Restasis is prescribed to increase tear production in chronic dry eye associated with inflammation. The different oral products are not freely interchangeable and require monitoring.
What are the side effects?
According to the prescribing information, common side effects of systemic use include:
- High blood pressure
- Kidney impairment with rising creatinine
- Tremor
- Excess hair growth and gum overgrowth
More serious considerations include:
- Boxed warnings for kidney toxicity and for increased risk of serious infections and cancers, including lymphoma and skin cancer
- The need for blood-level monitoring and attention to many drug interactions
- Restasis, acting locally, mainly causes eye burning or stinging and does not carry these systemic warnings
More for immune & defense
Sources: FDA prescribing information for Sandimmune, Neoral, and Restasis; the Canadian Multicentre Transplant Study (The New England Journal of Medicine, 1983, DOI: 10.1056/NEJM1983100630914011), indexed on PubMed. This document is educational and does not constitute medical advice.