Phase 2 Trial for Binimetinib for Patients With Relapsed/Refractory BRAF Wild Type Hairy Cell Leukemia and Variant

  • End date
    Jul 31, 2024
  • participants needed
  • sponsor
    National Cancer Institute (NCI)
Updated on 25 October 2022



Most people with hairy cell leukemia have a BRAF gene mutation. They can be treated with BRAF inhibitors, drugs that target this mutation. For people who do not have this mutation, BRAF inhibitors are not a treatment option. We found that in hairy cell leukemia, when BRAF is not mutated, the MEK gene frequently is. Binimetinib is a MEK inhibitor which targets MEK. It is important to determine if this drug can be a good treatment option in those who cannot benefit treatment with BRAF inhibitors.


To see if binimetinib is an effective treatment for hairy cell leukemia that does not have a BRAF mutation.


People ages 18 and older with hairy cell leukemia without a mutation in the BRAF gene and whose disease either did not respond to treatment or came back after treatment


Participants will be screened with:

  • Medical history
  • Physical exam
  • Blood and urine tests
  • Lung and heart tests
  • Eye exam
  • Bone marrow biopsy: A needle will be injected through the participant s skin into the bone to remove a sample of marrow.
  • CT or MRI scan: Participants will lie in a machine that takes pictures of the body. They might receive a contrast agent by vein.

Before they start treatment, participants will have an abdominal ultrasound, pulmonary function tests, and exercise stress tests.

Participants will take binimetinib by mouth twice daily in 28-day cycles. They will keep a medication diary.

Participants will have at least one visit before every cycle. Visits will include repeats of some screening tests.

Participants may continue treatment as long as their disease does not get worse and they do not have bad side effects.

About a month after their last dose of treatment, participants will have a follow-up visit. They will then have visits once a year.



  • Hairy cell leukemia (HCL) is an indolent B-cell leukemia comprising 2% of all leukemias, or approximately 1900 new cases per year in the US.
  • BRAF V600E mutation is very common in classic HCL.
  • HCL variant (HCLv) is wild type for BRAF and is more aggressive compared to classic HCL due to its lower response and shorter duration of response to standard purine analog chemotherapy. The median survival is only ~6 years compared to >25 years for classic HCL.
  • CD25+ classic-appearing HCL-cells that express unmutated IGHV4-34+ immunoglobulin rearrangement, are wild-type for BRAF, and confer a poor prognosis when treated with standard purine analog chemotherapy.
  • While BRAF and MEK combination inhibition is making an impact in the treatment of BRAF V600E mutated HCL, this treatment is not applicable for patients with BRAF-WT HCL/HCLv. Furthermore, with poor survival outcomes in this patient population, lack of targeted therapy constitutes a clear unmet need.
  • Recently, several BRAF WT HCL/HCLv patients have received MEK inhibitors by compassionate use and have had lifesaving partial to complete remission, however the response has not been assessed systematically in clinical trials.
  • Binimetinib (also known as MEK162) is an orally bioavailable, selective and potent mitogenactivated protein (MAP) kinase kinase (MEK1 and MEK2) inhibitor, which is approved for use in combination with encorafenib for the treatment of patients with BRAF-mutant melanoma
  • We have described MAP2K1 (MEK) mutations which may drive the aggressive clinical behavior of BRAF WT HCL/HCLv patients, but MEK inhibition may be clinically useful even in these patients without known MAP2K1 (MEK) mutations.

-To determine the overall response rate (ORR) to binimetinib, in participants with BRAF WT HCL and HCLv.

  • BRAF WT HCL or HCLv with at least 1 prior purine analog treatment
  • Need for treatment as evidenced by any one of the following: ANC <1 x10^3/mcL, Hgb <10g/dL, Platelet count <100 x10^3/mcL, leukemia cell count >5 x10^3/mcL, symptomatic splenomegaly, enlarging HCL mass > 2cm in short axis.
  • Greater than or equal to 18 years of age
  • No uncontrolled infection, cardiopulmonary dysfunction, or secondary malignancy requiring treatment.
  • No chemotherapy, immunotherapy, investigational agent or radiotherapy within 4 weeks prior to the start of study treatment.
  • Single arm phase 2 trial to determine ORR in participants with relapsed/refractory BRAF WT HCL and HCLv.
  • 2-phase minimax design will be used to rule out an unacceptable 10% in favor of an improved 25% ORR.
  • Initially 16 evaluable participants will be enrolled. If 2 or more achieve a major response, then accrual will continue to a total of 31 evaluable participants.
  • Binimetinib will be given at a dose of 45mg BID for as long as participants can continue dosing chronically without significant toxicity.

Condition Hairy Cell Leukemia
Treatment Binimetinib
Clinical Study IdentifierNCT04322383
SponsorNational Cancer Institute (NCI)
Last Modified on25 October 2022


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