Complex sentence: The withdrawal of Eraldin ® gave ICI the nudge to launch another β-blocker, atenolol, which was launched in 1976 under the trade name Tenormin ®.
Split into simpler sentences: The withdrawal of Eraldin ® gave ICI the nudge to launch another β-blocker. Atenolol was chosen and was launched in 1976 under the trade name Tenormin ®.