Low-Dose Danazol for the Treatment of Telomere Related Diseases

  • End date
    Oct 29, 2027
  • participants needed
  • sponsor
    National Heart, Lung, and Blood Institute (NHLBI)
Updated on 6 September 2023



DNA is a structure in the body. It contains data about how the body develops and works. Telomeres are found on the end of chromosomes in DNA. Some people with short telomeres or other gene changes can develop diseases of the bone marrow, lung, and liver. Researchers want to see if low doses of the hormone drug danazol can help.


To study the safety and effect of low dose danazol.


People ages 3 and older with a telomere disease who have either very short telomeres and a specific gene change. They must also show signs of aplastic anemia, lung, or liver disease.


Participants will be screened in another protocol.

Participants will have:

  • Medical history
  • Physical exam
  • Blood tests
  • Lung exam. They will breathe into an instrument that records the amount and rate of air breathed in and out over a period of time.

6-minute walking test.

  • Abdominal ultrasound and liver scan. These tests use sound waves to measure the fibrosis in the liver.

Some participants will have:

  • Pregnancy test
  • Small sample of the liver removed
  • Bone marrow biopsy. The bone will be numbed and a small needle will take a sample of the marrow.

All participants will have hormone levels checked.

All child participants will see a pediatric endocrinologist. Children may need to have a hand x-ray.

We will monitor patients for 6 months before starting danazol.

Participants will take danazol by mouth twice a day for 1 year.

Participants must return to the clinic at 6 months and 12 months while on danazol and 6 months after stopping it. They will have blood and urine tests, a lung exam, abdominal ultrasound, and liver scan.


Telomere disease is caused by accelerated telomere attrition and results in multi-organ dysfunction. Telomeres are nucleotide repeats of non-coding DNA at the end of the chromosomes which function as protective caps to prevent erosion of genomic DNA during cell division and to protect chromosomes from recognition as single stranded DNA. Telomeric DNA is elongated by the telomerase complex, which is comprised of a reverse transcriptase catalytic subunit (encoded by TERT), an RNA template (encoded by TERC) and associated proteins.

Telomerase activity is crucial in maintaining telomere length in cells with a high proliferative capacity, such as hematopoietic stem cells (HSCs) and lymphocytes. Presentation of telomeropathies can vary from severe aplastic anemia (SAA) and dyskeratosis congenital (DKC) early in childhood, to pulmonary or hepatic fibrosis later in life. There is no standard of care for the treatment of telomere disease.

Considerable evidence suggests that sex hormones regulate telomerase. Calado et al. demonstrated that human lymphocytes and CD34+ hematopoietic cells up regulate both TERT gene expression and telomerase enzymatic activity in response to androgens in vitro. A recent observational cohort study demonstrated hematologic response in 14 of 16 pediatric patients with DKC treated with androgens. In a prospective trial from our Branch, Townsley et al demonstrated that patients with telomere diseases who were treated with the synthetic sex hormone danazol showed telomere elongation, and hematologic response were seen in 79% of patients after only three months of treatment. This study used the highest dose of danazol, 800 mg daily, and known adverse effects, such as elevated liver enzyme levels and muscle cramps, occurred in 41% and 33% of patients, respectively. Overall the treatment was well tolerated, but some patients did require dose reduction. After 27 patients were enrolled, the study was halted early, because telomere attrition was reduced in all 12 patients who could be evaluated for the primary endpoint. Because of the limited power, we were unable to draw definitive conclusions regarding further clinical effect of danazol but stabilization or improvement was observed in a few cases in other organ function, measured by DLCO for pulmonary fibrosis and Fibroscan for cirrhosis.

We now propose a phase II study designed to determine the efficacy of low dose danazol in decreasing the rate of telomere attrition in subjects with a short age-adjusted telomere length. The secondary aim is to determine the clinical effect of this therapy in conditions that are related to short telomeres, to include cytopenia(s), pulmonary fibrosis, and/or hepatic fibrosis.

Condition Telomere Disease
Treatment Danazol
Clinical Study IdentifierNCT03312400
SponsorNational Heart, Lung, and Blood Institute (NHLBI)
Last Modified on6 September 2023


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