Pimecrolimus

Pimecrolimus is an immunomodulating agent used in the treatment of atopic dermatitis (eczema). It is currently available as a topical cream, once marketed by Novartis (however Galderma is promoting the compound in Canada since early 2007) under the trade name Elidel.

Pharmacology
Pimecrolimus is an ascomycin macrolactam derivative. It has been shown in vitro that pimecrolimus binds to macrophilin-12(also referred to as FKBP-12) and inhibits calcineurin. Thus pimecrolimus inhibits T-cell activation by inhibiting the synthesis and release of cytokines from T-cells. Pimecrolimus also prevents the release of inflammatory cytokines and mediators from mast cells.

General characteristics
Pimecrolimus, like tacrolimus, belongs to the ascomycin class of macrolactam immunosuppressives, acting by the inhibition of T-cell activation by the calcineurin pathway and inhibition of the release of numerous inflammatory cytokines, thereby preventing the cascade of immune and inflammatory signals. Pimecrolimus has a similar mode of action to that of tacrolimus but is more selective, with no effect on dendritic (Langerhans) cells. It has lower permeation through the skin than topical steroids or topical tacrolimus although they have not been compared with each other for their permeation ability through mucosa. In addition, in contrast with topical steroids, pimecrolimus does not produce skin atrophy. It has been proven to be effective in various inflammatory skin diseases, e.g., seborrheic dermatitis, cutaneous lupus erythematosus, oral lichen planus,  vitiligo, and psoriasis. Tacrolimus and pimecrolimus are both calcineurin inhibitors and function as immunosuppressants.

Side effects
See also: Immunomodulators in the treatment of eczema

In January 2006, the United States Food and Drug Administration (FDA) announced that Elidel packaging would be required to carry a black box warning regarding the potential increased risk of lymph node or skin malignancy, as for the similar drug tacrolimus. Whereas current practice by UK dermatologists is not to consider this a significant real concern and they are increasingly recommending the use of such new drugs.

Importantly, although the FDA has approved updated black-box warning for tacrolimus and pimecrolimus, the recent report of the American Academy of Dermatology Association Task Force finds that there is no causal proof that topical immunomodulators cause lymphoma or nonmelanoma skin cancer, and systemic immunosuppression after short-term or intermittent long-term topical application seems an unlikely mechanism. Another recent review of evidence concluded that postmarketing surveillance shows no evidence for this systemic immunosuppression or increased risk for any malignancy. However, there are still some strong debates and controversies regarding the exact indications of immunomodulators and their duration of use in the absence of active controlled trials. Dermatologists' and Allergists' professional societies, the American Academy of Dermatology, and the American Academy of Allergy, Asthma, and Immunology, have protested the inclusion of the black box warning. The AAAAI states "None of the information provided for the cases of lymphoma associated with the use of topical pimecrolimus or tacrolimus in AD indicate or suggest a causal relationship.".