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Evidence: HighPeptideFDA ApprovedCyclic 11-amino-acid peptideFDA-approved 1983 · SandimmuneCalcineurin inhibitor

Cyclosporine

The fungal cyclic peptide that made organ transplantation routine

Cyclosporine is a ring of 11 amino acids made by a soil fungus. It blocks calcineurin inside T cells, and in 1983 it became the drug that turned organ transplantation into routine care. It is also used for severe autoimmune disease and, as eye drops, for dry eye.

At a Glance Read Research →
Overview

What is it?

Cyclosporine was found in the 1970s in a fungus from a soil sample, and its ability to suppress the immune system without killing bone marrow cells set it apart from earlier drugs. It binds a protein called cyclophilin, and the pair blocks calcineurin, an enzyme T cells need to switch on interleukin-2. FDA approved it as Sandimmune in 1983.

Its arrival changed transplant medicine. In a 1983 trial of 209 kidney recipients, one-year graft survival was 80.4% on cyclosporine against 64.0% on the azathioprine-based standard. Neoral, a better-absorbed formulation approved in 1995, is not interchangeable with Sandimmune milligram for milligram, which the labels stress.

The price of that power is toxicity. The labels warn of kidney damage, high blood pressure, infections and cancers, and many drug interactions through CYP3A4; blood levels are monitored. Grapefruit raises levels. As eye drops, the dose reaching the blood is tiny, and the drops treat the inflammation behind chronic dry eye.

Structured data

At a Glance

Every value in this table is printed from the Grey Peptides dataset, the same record the compound explorer and comparison tool read, so the three can never disagree.

ClassA cyclic peptide of 11 amino acids made by a soil fungus, the first calcineurin inhibitor; approved in the US since 1983 to prevent organ transplant rejection, later for severe rheumatoid arthritis and psoriasis, and as eye drops for dry eye.
FormulaC62H111N11O12
Molecular weight1202.6 g/mol
Half-lifeterminal half-life about 8.4 hours (range 5 to 18) in blood
US statusFDA Approved
Evidence levelHigh
Last reviewed2026-10-03
Interactive

Half-Life: How Much Remains

The dataset records a half-life of terminal half-life about 8.4 hours (range 5 to 18) in blood for Cyclosporine. After each half-life, half of what was in the circulation is gone, so about 3% remains after five. Real clearance varies with the person, the dose, the route and kidney or liver function; this is arithmetic on a published figure, not a dosing tool.

Time since a single dose
ElapsedTimeRemaining
1 half-life8.4 h50% remaining
2 half-lives16.8 h25% remaining
3 half-lives25.2 h12.5% remaining
4 half-lives33.6 h6.25% remaining
5 half-lives42 h3.125% remaining
Evidence

Published Research

The studies behind cyclosporine, from their PubMed abstracts.

Human1983

The transplant trial that changed the field

In 209 cadaveric kidney recipients, predicted one-year graft survival was 80.4% with cyclosporine and prednisone against 64.0% with azathioprine-based standard therapy (P = 0.003), and patient survival 96.6% against 86.4%.

PMID: 6350878
Human1998

Neoral against Sandimmune

In a randomised double-blind study in kidney recipients, more patients on Sandimmune needed dose increases to keep blood levels in range in the first 3 months; blood pressure, creatinine and cyclosporine-related adverse events did not differ.

PMID: 9645802
Human1995

Added to methotrexate in rheumatoid arthritis

In severe rheumatoid arthritis not controlled by methotrexate, adding cyclosporine improved tender and swollen joint counts by 25% against placebo, with gains in pain, disability and global disease activity.

PMID: 7791814
Human2000

Eye drops for dry eye

In two multicentre randomised trials, cyclosporine 0.05% and 0.1% eye emulsions gave significantly greater improvement than vehicle in corneal staining and Schirmer tear values, two objective signs of moderate to severe dry eye.

PMID: 10768324
Review2002

How it was discovered

An account of cyclosporine's discovery in a fungal soil sample at Sandoz and its early pharmacology, including the finding that it suppressed lymphocytes without the bone-marrow toxicity of earlier immunosuppressants.

PMID: 12422576
Safety

Side Effects & Contraindications

Reported Side Effects

From the studies above.

● Kidney function changes and high blood pressure, monitored through treatment
● Adverse events comparable between the two oral formulations in the 1998 trial

Contraindications & Cautions

Warnings from the Sandimmune and Neoral labels (DailyMed, read October 3, 2026).

● Boxed warning: to be prescribed by physicians experienced in immunosuppression; Sandimmune and Neoral are not interchangeable without monitoring
● Kidney damage and high blood pressure
● Serious infections and cancers, including lymphoma and skin cancer
● Many drug interactions; grapefruit raises blood levels
Questions

Frequently Asked Questions

?Is cyclosporine a peptide?

Yes. It is a ring of 11 amino acids made by a fungus, including several unusual ones, which is why it survives digestion well enough to work as a capsule.

?What is the difference between Sandimmune and Neoral?

Neoral is a modified formulation that is absorbed more consistently. The labels say the two are not interchangeable milligram for milligram, so switching needs blood-level monitoring.

?Is Restasis the same drug?

Restasis is cyclosporine as an eye emulsion for chronic dry eye. Very little reaches the bloodstream, so it does not carry the systemic risks of the capsules.

Bibliography

References

  1. [fda] US FDA, Drugs@FDA (openFDA): SANDIMMUNE, NDA 050573 (November 14, 1983); NEORAL, NDA 050715 (July 14, 1995); RESTASIS, NDA 050790 (December 23, 2002). Read October 3, 2026.
  2. [fda-pi] FDA. Sandimmune (cyclosporine) US prescribing information (DailyMed set 5e5926a7-1de0-4b54-a5c0-286b6200ff82, effective July 10, 2026). Read October 3, 2026.
  3. [fda-pi] FDA. Neoral (cyclosporine, modified) US prescribing information (DailyMed set 94461af3-11f1-4670-95d4-2965b9538ae3, effective August 10, 2026). Read October 3, 2026.
  4. [clinical-trial] "A randomized clinical trial of cyclosporine in cadaveric renal transplantation." N Engl J Med, 1983;309(14):809-15. PMID: 6350878.
  5. [clinical-trial] Tugwell P, et al. "Combination therapy with cyclosporine and methotrexate in severe rheumatoid arthritis. The Methotrexate-Cyclosporine Combination Study Group." N Engl J Med, 1995;333(3):137-41. PMID: 7791814.
  6. [clinical-trial] Sall K, et al. "Two multicenter, randomized studies of the efficacy and safety of cyclosporine ophthalmic emulsion in moderate to severe dry eye disease. CsA Phase 3 Study Group." Ophthalmology, 2000;107(4):631-9. PMID: 10768324.
  7. [clinical-trial] Frei UA, et al. "Randomized, double-blind, one-year study of the safety and tolerability of cyclosporine microemulsion compared with conventional cyclosporine in renal transplant patients. International Sandimmun Neoral Study Group." Transplantation, 1998;65(11):1455-60. PMID: 9645802.
  8. [pubmed] Borel JF. "History of the discovery of cyclosporin and of its early pharmacological development." Wien Klin Wochenschr, 2002;114(12):433-7. PMID: 12422576.

Sources & Citations

Studies were read from their PubMed records; regulatory sources are listed below, read October 3, 2026.

Medical Disclaimer: This content is for educational and informational purposes only. It is not medical advice, and nothing here is an instruction to obtain or use any compound. Consult a licensed healthcare provider before making health decisions.

Last reviewed: 2026-10-03