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Last Updated: 04/06/22

Information below provided by the Pharmaceutical Company.


Agent Description

Mirdametinib is an investigational oral, allosteric, small molecule MEK inhibitor. Mirdametinib has the chemical name: N-[(2R)-2,3-dihydroxypropoxyl]-3,4-difluro-2-[(2-fluoro-4-iodophenyl)amino]benzamide. It has a molecular formula of C16H14N2O4F3I and a molecular mass of 482.2.

Mirdametinib is a white to tan or pink solid. It is orally administered as capsules, containing the active ingredient (mirdametinib) and compendial excipients (microcrystalline cellulose, croscarmellose sodium, magnesium stearate). Hard capsules composed of gelatin and precedented colorants are used. In addition to capsules, immediate release dispersible tablets containing the same components as the mirdametinib capsules, with the addition of natural grape flavor and sucralose for palatability, are also available.

Mechanism of Action

Mirdametinib is a highly selective non-ATP-competitive inhibitor of MEK1 and MEK2. As a potent MEK inhibitor, mirdametinib significantly inhibits the phosphorylation of the MAP kinases ERK1 and ERK2, leading to impaired tumor cell growth in vitro and in vivo. Preclinical in vivo pharmacology studies demonstrate that mirdametinib treatment leads to significant tumor growth inhibition and regression in tumor models dependent on the MAPK pathway for growth and survival, including those that harbor BRAF or RAS mutations.


MEK1/2 inhibitor

Molecular Targets



Mirdametinib, an investigational oral, allosteric, small molecule MEK inhibitor, is currently under development as a monotherapy in patients with Neurofibromatosis Type 1 Associated Plexiform Neurofibromas (NCT03962543). It is being evaluated as a monotherapy in a Phase 1/2 study in pediatric and adolescent patients with low-grade gliomas (NCT04923126).

Mirdametinib is also being investigated as monotherapy or in combination in biomarker-defined cancers owing to the critical role that the MAPK pathway plays in the growth and proliferation of many cancer types (including lung cancer, melanoma, pancreatic cancer, colorectal cancer, endometrial cancer, and ovarian cancer).

A Phase 1b/2 clinical trial is being conducted in collaboration with BeiGene to evaluate mirdametinib in combination with lifirafenib, a RAF dimer inhibitor, in patients with advanced or refractory solid tumors that harbor RAS mutations, RAF mutations, and other MAPK pathway aberrations (NCT03905148).

In addition, under a SpringWorks-supported investigator-initiated clinical trial agreement with Memorial Sloan Kettering Cancer Center, a Phase 1b/2a study is evaluating mirdametinib in combination with fulvestrant, a selective estrogen receptor degrader (SERD), in patients with ER+ metastatic breast cancer harboring NF1 loss-of-function or other alterations of the MAPK pathway, and as a monotherapy in adult patients with advanced solid cancers harboring MEK1 or MEK2 mutations (NCT05054374).

Studies of Interest

Areas of Interest:

  • Exploration of mirdametinib as monotherapy or rational combinations with other therapies in preclinical models and/or in the clinic in disease indications that are supported by scientific rationale.
  • Studies to delineate mechanisms of response or resistance to mirdametinib treatment and/or to optimize treatment response.

Information collaborator would like included in investigator proposals