Shares of the clinical-stage cancer immunotherapy company Iovance Biotherapeutics (NASDAQ: IOVA) cratered today in response to a presentation at the H.C. Wainwright Global Investor Conference in New York City yesterday. What specific event triggered this downward spiral?Investors apparently aren't thrilled with the company's clinical update for its mid-stage tumor-infiltrating lymphocyte (TIL) therapy, C-144-01, in patients with advanced skin cancer who have been previously treated with an anti-PD-1 and anti-CTLA-4 checkpoint inhibitor. As of 2:29 p.m.