Siklos Now Approved in US for Adults With Sickle Cell Anemia

Marisa Wexler, MS avatar

by Marisa Wexler, MS |

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Siklos (hydroxyurea) is now approved in the U.S. to reduce the frequency of painful crises and lower the need for blood transfusions in adults with sickle cell anemia, the most common and usually the most severe form of sickle cell disease.

The medication already was approved for the same indications in children ages 2 and older.

“Siklos has been a valuable and effective treatment option for children so it is very useful to now have it available for them to continue as they grow into adults,” Wally Smith, MD, the director of the adult sickle cell disease program at Virginia Commonwealth University, said in a press release.

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An oral medicine, Siklos is available as 100 mg scored tablets and triple-scored 1,000 mg tablets, designed so they can be cut into smaller pieces. This allows for more flexible dosing, according to Medunik USA, the company that markets the therapy.

“Besides being a new treatment option for adults, Siklos has the advantage of being the only formulation of hydroxyurea available in breakable tablet form that can be dissolved in a small amount of water for those who have difficulty swallowing pills or capsules,” Smith said.

“Medunik USA is very proud to expand the availability of Siklos as a new treatment option for adults with sickle cell anemia as part of our commitment to help Americans suffering from rare diseases. They deserve to have effective treatment options as much as those with more common conditions,” said Tanya Carro, executive vice president of Medunik USA.

Sickle cell is caused by mutations that impact the production of hemoglobin, the protein that red blood cells use to carry oxygen through the body.

The active agent in Siklos, hydroxyurea, is thought to work by promoting an alternate version of the protein fetal hemoglobin to be produced to compensate for the defective protein. As its name suggests, fetal hemoglobin usually is produced only in early development and stops being made within a few months after birth.

The approval of the therapy in adults was supported by data from a Phase 4 observational trial called ESCORT-HU (NCT02516579), which evaluated the safety of Siklos in more than 1,000 adults with sickle cell disease. Among these patients, 370 were followed for at least one year.

Results indicated that a year of treatment with Siklos reduced the frequency of hospitalizations, blood transfusions, and vaso-occlusive crises lasting longer than two days, compared with the previous year.

No new safety issues were noted in the trial. There were 125 pregnancies in more than 100 women during the study with no malformations in the babies reported.

The most common side effects of Siklos include infections, headache, and dry skin in adults, and infections and low white blood cell counts in children. The medication carries a boxed warning that it can severely lower blood cell levels and increase the risk of cancer. Patients are encouraged to read the safety information included in the packaging.