Remember our discussions on gene editing and your interest in personalized medicine? Let's explore how CRISPR-Cas9 can be used to develop targeted therapies for individuals based on their genetic makeup. Discuss the challenges and ethical considerations of this approach. 
<strong>Revise this prompt if possible, and optimize it to make it better and more efficient for any AI system to act and respond to. 
If possible run your optimized version.</strong>