Cyclosporine: A Literature Course on What the Studies Report

About this course

This course is organised into six modules. Each one summarises a slice of the published cyclosporine literature — how studies were designed, what researchers measured, and what they reported — and each module closes with a short statement of what that evidence cannot show. Nothing here is a protocol, a comparison of options, or a suggestion that any reader should use anything. This page is for educational purposes only and is not medical advice; consult a licensed physician about any medicine, symptom or medical decision.

Cyclosporine appears in the literature under several spellings (cyclosporine, ciclosporin, cyclosporin A, CsA). This page treats them as the same molecule and uses the name that each cited paper used where relevant.

Module 1: What cyclosporine is and how it has been studied

Definition and class

Cyclosporine is a cyclic undecapeptide — a ring of eleven amino acids, several of them N-methylated and one of them unusual — originally isolated from a soil fungus. Because of that structure it is, strictly speaking, a peptide; it is not, however, a linear synthetic research peptide of the kind studied in metabolic or regenerative work. In clinical pharmacology it is classified as a calcineurin-inhibitor immunosuppressant, and the review literature places it among the systemic immunosuppressive agents used in transplantation and in inflammatory disease, including a dermatology-focused review of its role in skin disease (PMID 27319953).

Forms that appear in the literature

Published work has examined cyclosporine in several delivery forms. Intravenous administration was reported in inflammatory bowel disease (PMID 18251148). Topical ocular delivery has been reviewed in the setting of corneal transplantation (PMID 25357076). Oral systemic use dominates the transplantation literature, including clinical experience reports from transplant centres (PMID 15041307). Formulation science has continued: researchers developed a cyclosporine A nanosuspension and tested cytotoxicity and permeability on Caco-2 cell monolayers (PMID 34931593).

How the evidence base is shaped

The cyclosporine literature is unusually broad and unusually old. It includes decades of transplant experience, narrative reviews, case reports, small case series, and laboratory studies in cells and animal models. That mixture matters: a five-patient case series and a multi-year transplant programme report answer very different questions and carry very different weight.

Limits of the evidence in this module. Definitions and drug class are descriptive, not evidence of benefit. The verified papers summarised here do not constitute a systematic review, and the presence of a study on a given route of administration says nothing about how well that route performs relative to any other.

Module 2: Mechanism as described in the literature

The calcineurin pathway

Cyclosporine is described in the review literature as a calcineurin inhibitor — a drug that acts inside lymphocytes by binding an intracellular immunophilin and blocking calcineurin-dependent signalling, with downstream reduction of T-cell activation cytokines. A dermatology review framed this immunosuppressive mechanism as the basis for the agent's systemic use in inflammatory skin disease (PMID 27319953).

Effects on antigen-presenting cells

Mechanistic interest is not limited to T cells. Researchers examined the effects of cyclosporine on human dendritic cell subsets in a laboratory study, reporting that the drug's activity extended to these antigen-presenting populations rather than being confined to lymphocyte signalling alone (PMID 15808533).

Non-immune targets in microorganisms

Because the cyclophilin proteins cyclosporine binds are conserved across species, the molecule has also been studied outside immunology. An in vitro study reported that cyclosporine affected the main virulence factors of Cryptococcus neoformans, a pathogenic yeast, in culture (PMID 37108941). That is a laboratory observation about a microorganism, not a statement about treating infection in people.

Barrier crossing and cell tolerance

Mechanism also includes getting the molecule where it needs to go. In formulation work, researchers assessed a cyclosporine A nanosuspension for cytotoxicity and for permeability across Caco-2 intestinal epithelial cell lines, an established in vitro screen for oral absorption behaviour (PMID 34931593).

Limits of the evidence in this module. Mechanistic descriptions explain how a molecule is believed to act; they do not establish that any particular clinical result follows. Cell-culture findings — including dendritic cell, Caco-2 and fungal virulence work — occur at concentrations and conditions chosen by the investigators and do not translate directly to whole organisms.

Module 3: Reported outcomes, study by study

Transplantation

The transplant literature is where cyclosporine has been used and documented longest. A transplantation proceedings report described a centre's accumulated clinical experience with cyclosporine, summarising how the agent performed within an immunosuppressive regimen over time rather than testing it against a comparator in a randomised design (PMID 15041307).

Inflammatory bowel disease

In gastroenterology, researchers reported on intravenous cyclosporine in inflammatory bowel disease and characterised their experience, in the words of their own report title, as safe and effective in that setting (PMID 18251148). That is the authors' conclusion about their own cohort, not a general claim about outcomes for anyone else.

Dermatology and chronic urticaria

A dermatology review surveyed the indications, monitoring considerations and place of cyclosporine among systemic agents in skin disease (PMID 27319953). More narrowly, a 2023 report described five patients with chronic urticaria that had not responded to omalizumab and reported the clinical course observed after cyclosporine was introduced (PMID 37644553). Five patients, no control group, and no randomisation: this is hypothesis-generating documentation.

Ophthalmology

A review in Cornea examined topical cyclosporine in corneal transplantation, collecting what had been published about ocular surface delivery in graft settings (PMID 25357076).

Preclinical and laboratory endpoints

Animal and cell work has used cyclosporine both as the intervention and as the insult. In one nephrology study, cyclosporine A produced anemia and peritubular capillary loss in the experimental model, and researchers reported that daprodustat prevented those changes (PMID 35643373). In microbiology, the study of Cryptococcus neoformans measured virulence factor expression in vitro (PMID 37108941).

Limits of the evidence in this module. None of the clinical reports cited here is a large randomised controlled trial with a prespecified primary endpoint. Case series and experience reports cannot separate drug effect from natural disease course, concurrent therapy or selection of who was treated. Preclinical endpoints such as capillary density are not the same as patient-centred outcomes.

Module 4: Cyclosporine Side Effects: What Studies Report

Oral and dental findings

Gingival enlargement is one of the most consistently documented cyclosporine-associated findings. A periodontics report described management of cyclosporine-influenced gingival enlargement using azithromycin, documenting the overgrowth as a recognised consequence of exposure to the drug (PMID 32074404).

Neurological and vascular case reports

A 2023 case report in Practical Neurology described cyclosporine-induced erythromelalgia — episodic redness, warmth and burning pain in the extremities — attributed by the authors to the drug (PMID 37391230). Single case reports establish that an event was observed and considered drug-related; they do not establish frequency.

Hematologic and renal microvascular findings in models

In an experimental setting, researchers reported that cyclosporine A produced anemia and peritubular capillary loss, and that co-administration of daprodustat prevented both changes in that model (PMID 35643373).

Safety as characterised in clinical reports

Clinical reports have also framed tolerability positively within their own cohorts: the intravenous inflammatory bowel disease report described the approach as safe and effective in the patients studied (PMID 18251148), while a dermatology review discussed the monitoring that accompanies systemic use in skin disease (PMID 27319953).

Limits of the evidence in this module. Case reports and small series are not incidence data; no rate can be inferred from them. Reviews summarise other people's observations and inherit their gaps. A finding produced in an animal model may not occur in humans, and the absence of an adverse event from this list is not evidence that it does not occur — it only means the verified papers reviewed here did not report it.

Module 5: Pharmacokinetics where data exist

Absorption and formulation

Cyclosporine is a large, lipophilic cyclic peptide, and its absorption behaviour has long driven formulation research. Researchers who developed a cyclosporine A nanosuspension evaluated it for cytotoxicity and for permeability across Caco-2 cell monolayers, an in vitro proxy used to compare formulations before animal or human testing (PMID 34931593).

Distribution into biological fluids

One of the few human distribution datasets in the verified set concerns lactation. A 2020 study measured cyclosporine A and its metabolites in the colostrum of post-transplant mothers and reported low content of the parent drug and its metabolites in that fluid (PMID 32899873).

Local versus systemic exposure

Route shapes exposure. The review of topical cyclosporine in corneal transplantation addressed delivery to the ocular surface rather than systemic circulation (PMID 25357076), whereas the intravenous inflammatory bowel disease report and the transplant experience report describe systemic exposure settings (PMID 18251148, PMID 15041307).

Limits of the evidence in this module. No half-life, bioavailability percentage, clearance value or concentration target is stated on this page, because the verified papers assembled here do not supply those numbers in a form this page can responsibly quote. Caco-2 permeability is a screening model, not human pharmacokinetics, and colostrum measurements describe one fluid in one population.

Module 6: Regulatory status, stated factually

Approved products

Unlike most compounds covered in peptide education, cyclosporine is not an investigational or research-only molecule. It is an approved prescription drug in the United States, the European Union and many other jurisdictions, marketed in oral capsule, oral solution, intravenous concentrate and ophthalmic emulsion forms, under both brand and generic labels. Approved indications historically centre on prophylaxis of organ rejection in transplantation, with additional dermatologic, rheumatologic and ophthalmic indications depending on the specific product and country. The published clinical literature cited in this course includes uses that fall inside and outside those labelled indications, such as intravenous administration in inflammatory bowel disease (PMID 18251148) and topical use around corneal grafting (PMID 25357076).

Research-use-only material

Cyclosporine A is also sold as a research-use-only laboratory reagent for in vitro work — the category of material used in studies such as the dendritic cell subset experiments (PMID 15808533) and the Cryptococcus neoformans virulence work (PMID 37108941). Research-grade material is labelled for laboratory use, is not manufactured to pharmaceutical standards, and is not intended for human or veterinary administration.

Compounding

In the United States, compounded preparations are governed by sections 503A (traditional pharmacy compounding for an identified patient with a prescription) and 503B (outsourcing facilities) of the Federal Food, Drug, and Cosmetic Act. Compounded ophthalmic cyclosporine preparations have a long history in eye care, predating and coexisting with commercially approved emulsions; the corneal transplantation review sits in that topical context (PMID 25357076). Rules on what may be compounded change over time and vary by jurisdiction. This section is regulatory background, not legal advice.

Limits of the evidence in this module. Regulatory approval reflects a sponsor's submitted dossier for a specific product, formulation and indication; it is not a general endorsement of the molecule for other uses, and approval status differs between countries and between product forms.

What the studies did not test

Across the verified literature summarised here, several questions remain unanswered:

• Use in healthy people. Every clinical report cited involved patients with transplants, inflammatory bowel disease, urticaria, skin disease or eye disease — for example the five-patient urticaria series (PMID 37644553). None studied healthy volunteers seeking enhancement or wellness endpoints.
• Head-to-head comparisons. The cited reports did not randomise cyclosporine against alternative agents with blinded assessment.
• Long-term adverse event rates. Gingival enlargement (PMID 32074404) and erythromelalgia (PMID 37391230) appear as reports of observed events, not as denominators in a cohort.
• Translation of laboratory findings. Effects on fungal virulence factors (PMID 37108941) and on Caco-2 permeability (PMID 34931593) were measured in vitro and were not tested as clinical outcomes.
• Infant exposure outcomes. The colostrum study measured drug content in that fluid (PMID 32899873); it did not follow infant clinical outcomes as an endpoint on this page's reading.

Readers comparing this course with other sources should note that cyclosporine has a very large literature beyond these twelve papers. The purpose here is to model how to read studies — design first, endpoint second, conclusion last — not to summarise every publication. This page is for educational purposes only and is not medical advice; consult a licensed physician for any personal medical question.

References

• Cyclosporine-induced erythromelalgia (Practical Neurology, 2023)
• Cyclosporine in Dermatology (Skinmed, 2016)
• Daprodustat prevents cyclosporine-A-mediated anemia and peritubular capillary loss (Kidney International, 2022)
• Experience with cyclosporine (Transplantation Proceedings, 2004)
• Development of cyclosporine A nanosuspension: cytotoxicity and permeability on Caco-2 cell lines (Pharmaceutical Development and Technology, 2022)
• Cyclosporine Affects the Main Virulence Factors of Cryptococcus neoformans In Vitro (Journal of Fungi, 2023)
• Cyclosporine for omalizumab-refractory chronic urticaria: a report of five cases (Allergy, Asthma and Clinical Immunology, 2023)
• Low Content of Cyclosporine A and Its Metabolites in the Colostrum of Post-Transplant Mothers (Nutrients, 2020)
• Effects of cyclosporine on human dendritic cell subsets (Transplantation Proceedings, 2005)
• Topical cyclosporine in corneal transplantation (Cornea, 2015)
• Intravenous cyclosporine for inflammatory bowel disease--safe and effective (Hepato-Gastroenterology, 2007)
• Management of Cyclosporine-Influenced Gingival Enlargement With Azithromycin (Clinical Advances in Periodontics, 2020)