Gilead deal could add up to $6.3B for Tango

Tango Therapeutics has struck a new deal with its longtime drug development partner worth upwards of $6.3 billion — and the startup’s chief executive is confident it can hit the mark and collect the full financing.  California biotech giant Gilead Sciences (Nasdaq: GILD) has re-negotiated its deal with local startup Tango Therapeutics, boosting the number of drugs targets the two could work on from five to 15. In turn, Gilead has made a $150 million upfront payment, a $20 million equity investment…