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Clinical Trial
, 374 (20), 1922-31

Danazol Treatment for Telomere Diseases

Clinical Trial

Danazol Treatment for Telomere Diseases

Danielle M Townsley et al. N Engl J Med.


Background: Genetic defects in telomere maintenance and repair cause bone marrow failure, liver cirrhosis, and pulmonary fibrosis, and they increase susceptibility to cancer. Historically, androgens have been useful as treatment for marrow failure syndromes. In tissue culture and animal models, sex hormones regulate expression of the telomerase gene.

Methods: In a phase 1-2 prospective study involving patients with telomere diseases, we administered the synthetic sex hormone danazol orally at a dose of 800 mg per day for a total of 24 months. The goal of treatment was the attenuation of accelerated telomere attrition, and the primary efficacy end point was a 20% reduction in the annual rate of telomere attrition measured at 24 months. The occurrence of toxic effects of treatment was the primary safety end point. Hematologic response to treatment at various time points was the secondary efficacy end point.

Results: 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 end point; in the intention-to-treat analysis, 12 of 27 patients (44%; 95% confidence interval [CI], 26 to 64) met the primary efficacy end point. Unexpectedly, almost all the patients (11 of 12, 92%) had a gain in telomere length at 24 months as compared with baseline (mean increase, 386 bp [95% CI, 178 to 593]); in exploratory analyses, similar increases were observed at 6 months (16 of 21 patients; mean increase, 175 bp [95% CI, 79 to 271]) and 12 months (16 of 18 patients; mean increase, 360 bp [95% CI, 209 to 512]). Hematologic responses occurred in 19 of 24 patients (79%) who could be evaluated at 3 months and in 10 of 12 patients (83%) who could be evaluated at 24 months. Known adverse effects of danazol--elevated liver-enzyme levels and muscle cramps--of grade 2 or less occurred in 41% and 33% of the patients, respectively.

Conclusions: In our study, treatment with danazol led to telomere elongation in patients with telomere diseases. (Funded by the National Institutes of Health; number, NCT01441037.).


Figure 1
Figure 1. Changes in Telomere Length in Patients Receiving Danazol
Panel A shows the telomere length measured at 24 months (the time point used for evaluation of the primary end point) in 12 patients, plotted against each patient’s baseline telomere measurement. The points above the dotted line represent patients who met the protocol-defined primary efficacy end point, a telomere attrition rate of 96 bp per year or less. Data for 15 patients were missing at 24 months; in the analysis of the primary end point, these patients were considered as not having had a response. In Panel B, summary statistics are shown in box plot format for changes in telomere length at landmark visits, as compared with baseline; the line within each box indicates the median, the top and bottom edges the 75th and 25th percentiles, respectively, and the I bars the range. The light dashed-and-dotted line represents the anticipated rate of telomere attrition with age in healthy persons (60 bp per year), and the bold dashed line represents the anticipated rate of attrition in patients with telomere diseases (120 bp per year). All patients who could be evaluated had improvements in telomere attrition while receiving danazol. Significant telomere elongation was found at 6, 12, and 24 months after the initiation of treatment with danazol, as compared with baseline. When treatment with danazol was stopped at 24 months, a decrease in telomere length was observed at 30 months and 36 months. All available data points were used in this analysis.
Figure 2
Figure 2. Hematologic Response in Patients Treated with Danazol, According to Mutation
For each landmark visit, the hematologic response to danazol is shown, with all patients listed according to patient number (UPN) on the left and genomic position of the heterozygous telomere gene mutation at right. Mutations were not detected in 6 patients despite screening for all known genes that have been reported to be mutated in telomere diseases (CTC1, DKC1, NOP10, NHP2, RTEL1, TERC, TERT, WRAP53, TINF2, and USB1). No data were available for 15 patients at 24 months: 10 withdrew from the study, and 5 had not reached the 2-year time point for evaluation of the primary end point because the study was halted early. An asterisk indicates that the pathogenicity was ambiguous; the p.Ala1062Thr and p.Glu280Lys variants have allele frequencies of 1.3% and 0.05%, respectively, in healthy controls (
Figure 3
Figure 3. Blood Counts in Patients with Telomeropathy Treated with Danazol
Peripheral-blood counts at various time points during the study are shown. Each symbol denotes a blood count in one patient; circles denote counts assessed during the period in which danazol was administered, and squares denote counts assessed after treatment with danazol was discontinued, per protocol, at 24 months. Black symbols denote counts in patients with a preexisting abnormally low value in that cell lineage, which was used to satisfy the enrollment criterion, and paired t-test results were performed for only these patients; gray symbols denote counts in all other patients in the study. The enrollment criterion for protocol entry was anemia (hemoglobin level, <9.5 g per deciliter, or substantial requirements for red-cell transfusions), thrombocytopenia (platelet count, <30,000 per cubic millimeter, or <50,000 per cubic millimeter with bleeding), or neutropenia (absolute neutrophil count, <1000 per cubic millimeter) (summary statistics are provided in Tables S5 and S6 in the Supplementary Appendix).

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