Derry came from two goals down to save a vital point in their quest for the title.
A late own-goal by Drogheda United keeper Robert Duggan was reward for incessant City pressure in the second half as they fought bravely back from two goals down at half time.
Drogheda took the lead with their first attack, Brian Gannon heading in from a Lee Lynch cross just three minutes in.
Derry responded but their luck was out in a period which saw them rattle the frame of Drogheda's goal three times.
Gareth McGlynn first saw his looping header bounce off the top of Duggan's crossbar before his audacious lobbed effort came back off the post.
City struck the woodwork again, this time Stephen McLaughlin seeing his drive crash off the upright.
Drogheda doubled their lead shortly afterwards, Brennan was left in space to beat Gerard Doherty with a looped shot.
The home side had to wait until 17 minutes from time for their first reply when Ruaidhri Higgins shot was deflected into the net by McGlynn.
That only spurred City on further and, when Duggan spilled a corner from McLaughlin, the unfortunate goalkeeper saw the ball hit off the back of his heel and end up in the net just three minutes from time as Stephen Kenny's side rescued a vital point.
Derry -- Doherty, Molloy, Greacen, McEleney (McBride, 80), Deery, McEleney (McDaid, 60), McGlynn, McLaughlin, Higgins, Zayed, Lafferty.
Drogheda -- Duggan, Gaul, Rogers, McNally, Clarke, Lynch, Gannon, McMahon, White, Hand (O'Brien, 79), Brennan.
Ref -- R Winter (Wicklow).