In Carella City, ageing can be postponed but not vanquished, until an exiled murderer helps a 157 year old woman evade her creator.

I wouldn’t bother with the city name, it adds nothing to the logline. I would consider changing this for something that tells us where Carella City is. Is it Earth: 2178? Or a parallel universe? Another planet? A galaxy far, far away?

Who’s the protagonist? The murderer or the old woman?

What’s the inciting incident? Is it the moment they realise she’s evaded death? Or is when these two first meet?

What’s the goal? To evade death? Or to protect this woman from the authorities so the secret doesn’t get out?

Why do we care about an exiled murderer? What was he exiled for? Maybe if he was a bio-engineer who was researching methods of immortality and accidentally killed someone we would be more sympathetic to his plight?

Other than death, who or what antagonistic forces are working against them? Why do we care if he doesn’t succeed in keeping her alive? (if that is his goal) She was going to die anyway right? We need to care about both of these characters and want them to achieve what they set out to do.

I feel like there’s a lot of information missing for me to understand what’s actually happening in this story. There’s definitely a story in there somewhere though.

After finding the woman he was exiled for murdering very much alive, a bio-engineer, tasked with finding the cure for death, must keep her alive long enough to uncover the conspiracy hiding the key to mankind’s immortality.?

This is long and a bit vague but there’s a strong connection between the inciting incident and the goal, internal and external motivation, stakes, antagonistic forces. No idea whether this is remotely close to the story you’re trying to tell though.

Hope this helps.