shares of immunogen are trading lower after the drugmaker said its chief medical officer is departing and raised its annual cost forecast as it spends more to support its cancer drug elahere the stock was down 86 at 1784 in midday trading shares have more than tripled this year the waltham massbased company said monday morning that chief medical officer anna berkenblit is stepping down in august to take a professional hiatus she will be succeeded by michael vasconcelles the companys executive vice president for research development and medical affairs immunogen also said that it now expects annual operating expenses of 350 million to 365 million this year an upward revision from its previous guidance due to increased spending in support of elahere which is preparing for a launch in europe