I believe their is a growing awareness of the effectiveness of Bayer's drug, and the fact that it's possible an NDA could be filed this year, or next year at the latest. A couple milestones could come into play by the time it's approved, and they could be substantial.
I doubt they're enough to handle all IMGN's financial needs before IMGN853 anticipates approval in 2020, so I also believe that investors, especially Institutions, may feel some degree of certainty that IMGN will partner one or more of it's wholly owned drugs in a timely manner.
I believe that if you take financial concerns off the table, IMGN ought to have a market cap that's between 25% and 50% of SGEN's where it traditionally sells for rather than a tiny fraction of SGEN's market cap.
Gary