Background: No drug treatment capable of restoring locomotor capabilities in patients suffering a
motor-complete spinal cord injury (SCI) has ever been developed. We assessed the safety and efficacy of an
activator of spinal locomotor neurons in humans, which were shown in paraplegic animals to elicit temporary
episodes of involuntary walking.
Methods: Single administration of buspirone/levodopa/carbidopa (SpinalonTM), levodopa/carbidopa (ratio 4: 1),
and buspirone or placebo was performed using a dose-escalation design in 45 subjects placed in supine position
who had had an SCI classified as complete (AIS A) or motor-complete/sensory incomplete (AIS B) for at least 3
months. Blood samples before and at regular intervals (15, 30, 60, 120, 240 min) after treatment were collected
for hematological and pharmacokinetic (PK) analyses. Electromyographic (EMG) activity of eight muscles (four
per leg) was monitored prior to and at several time points after drug administration.
Results: SpinalonTM (10-35 mg buspirone/100-350 mg levodopa/25-85 mg carbidopa) displayed no sign of safety
concerns - only mild nausea was found in 3 cases. At higher doses, 50 mg/500 mg/125 mg SpinalonTM was considered
to have reached maximum tolerated dose (MTD) since 3 out of 4 subjects experienced related adverse
events including vomiting. PK analyses showed comparable data between groups suggesting no significant drugdrug
interaction with SpinalonTM. Only the SpinalonTM–treated groups displayed significant EMG activity accompanied
by locomotor-like characteristics - that is with rhythmic and bilaterally alternating bursts.
Conclusion: Therefore, this study provides evidence of safety and preliminary efficacy following a single administration
of SpinalonTM in subjects with SCI.