Anxiety drugs such as Valium work well but produce side-effects that include drowsiness, forgetfulness and clumsiness and, when taken over time, can induce dependency.
The new compound, XBD173, appears to avoid these problems by targeting a different biological "don't panic" button, making it a good potential candidate for use as a safe and fast-acting anxiety pill.
Researchers published details of their experimental drug in the journal Science on Thursday, including encouraging results from an initial Phase I clinical study, which was sponsored by Swiss drugmaker Novartis.
A company spokesman said XBD173 was no longer in clinical development at Novartis but had been given to co-development partner Dainippon Sumitomo Pharma.
"What is needed right now is a rapid-acting anxiolytic (anxiety drug) that is effective but lacks the side effects of benzodiazepines," lead researcher Rainer Rupprecht of Munich's Ludwig Maximilian University said in a telephone interview.
"This shows that there is a possibility."
Roche's drug Valium, known generically as diazepam, is the best known of the benzodiazepine class of drugs, which have dominated the anxiety treatment market since the 1960s.
Antidepressants called selective serotonin reuptake inhibitors (SSRIs), such as Eli Lilly's Prozac, which is sold generically as fluoxetine, are also given for anxiety disorders but are of no use in acute episodes since they take several weeks to have an effect.
By contrast XBD173 worked within one hour of being given to rats in laboratory tests and also reduced panic in a week-long clinical study involving 70 healthy male volunteers given the new drug, an older benzodiazepine or a placebo.
The German team tested effectiveness by injecting subjects with a chemical called CCK-4 that is known to trigger a short-lived anxiety attack, which raises both heart rate and blood pressure.
They found that XBD173 produced a fast anti-anxiety response without any withdrawal symptoms after use.
The new compound works by promoting the synthesis of neurosteroids that modulate the effects of a brain chemical called GABA. Benzodiazepines also affect GABA, but in a different way.
Drug companies have been trying for some time to develop next-generation benzodiazepines by tweaking their chemical make-up to deliver a more selective effect that avoids unwanted side effects -- but it has proved an uphill struggle.
In 2003 Merck & Co abandoned one such drug, known as GABA Alpha 2/Alpha 3, after disappointing mid-stage clinical trials.
(Editing by Greg Mahlich)
By Ben Hirschler LONDON (Reuters) - German scientists believe they may have found a better anxiety drug that can counteract panic attacks without the side effects caused by existing treatments like Valium.