Dayna Ferdinadni, from Dystonia UK, said the study showed promise but more checks were needed.
“The drug has not yet been approved by NICE [National Institute for Health and Care Excellence] or the NHS for use in treating dystonia and further rigorous evaluation is needed to assess its safety, efficacy, and long-term impact,” she said.
“We welcome any research into dystonia, but it is crucial that new treatments undergo thorough scrutiny before being considered for widespread use.”
The causes of LD are not yet fully understood, the charity says, but vocal exercises and relaxation can help.
Symptoms often appear in midlife.
Kennedy, 70, says he had “a very strong voice” before developing LD, at 42.
He recently had “novel surgery” on his larynx (voice box), in Japan, which helped his voice, he says.
