Complex sentence: Theoretical considerations suggested TRIAC (triiodothyroacetate, a natural non-classical thyroid hormone) to be beneficial, however trials, where children were treated with TRIAC were unsuccessful, possibly because therapy was started too late.
Split into simpler sentences: Theoretical considerations suggested TRIAC (triiodothyroacetate, a natural non-classical thyroid hormone) to be beneficial. Trials, where children were treated with TRIAC were, however, unsuccessful, possibly because therapy was started too late.