Careful planning would probably include issuing Sec 1244 small business stock, which could subsequently qualify for an ordinary loss of up to $100K. Then you could close the corp to realize the loss- potentially as ordinary.

https://www.law.cornell.edu/uscode/text/26/1244 

Otherwise startup costs are limited to $5,000 under Sec. 195. The $5,000 deduction is reduced dollar for dollar (but not below zero) by the cumulative amount of startup costs exceeding $50,000. The remaining startup costs can be deducted ratably over a 15-year period once the active trade or business begins.