Can I transfer H1-B on OPT cap-gap while its still under approval?

I graduated from NYU with a Masters in May 2014. My opt ended on June 1st 2015. My employer has applied for my H1-B in April 2015 which was selected and is now under the approval process. I am currently on my cap-gap. Can I switch employers right now or do I need to wait till approval is there?.

Also Can I change employers on cap-gap or do I need to wait till October 1.

I have been in New York since last year.