Complex sentence: Many CCR5 antagonists have been introduced by pharmaceutical companies but few of them have actually reached human efficacy studies, for example AstraZeneca, Novartis, Merck and Takeda have used these GPRC compound collections to develop a potent CCR5 antagonist but none of them have reached clinical trials.
Split into simpler sentences: Many CCR5 antagonists have been introduced by pharmaceutical companies but few of them have actually reached human efficacy studies. For example AstraZeneca, Novartis, Merck and Takeda have used these GPRC compound collections to develop a potent CCR5 antagonist but none of them have reached clinical trials.