Mersana Therapeutics (MRSN) Plunges 5.23% Amid Drug Trial Data

Mersana Therapeutics (MRSN) shares plummeted 5.23% today, marking the second consecutive day of decline, with a total drop of 12.18% over the past two days. The stock price hit its lowest level since April 2025, experiencing an intraday decline of 9.09%.

The strategy of buying MRSN shares after they reached a recent low and holding for 1 week showed poor performance over the past 5 years. The cumulative return was -87.6%, significantly underperforming the market. This indicates that relying on recent lows as a buying trigger and holding for a short duration is not a viable strategy for MRSN.

One of the primary factors influencing Mersana Therapeutics' stock price is the progress of its drug candidate XMT-1660, which is currently in Phase 1 trials. This drug is targeting high unmet need tumors, including breast, endometrial, and ovarian cancers. On June 2, 2025, additional data was reported, which has likely influenced investor sentiment and contributed to the recent stock price movements.

Another significant factor is the change in short interest. Recently, the short interest in Mersana Therapeutics has decreased by 13.07%. This reduction suggests improving investor sentiment, which could positively impact the stock price. A lower short interest indicates that fewer investors are betting against the company, potentially signaling a more optimistic outlook.

Additionally, the high level of institutional ownership in Mersana Therapeutics is noteworthy. The current institutional ownership percentage stands at 93.92%, with 55 institutional buyers over the last 12 months. This high level of institutional ownership could signal confidence in the company's prospects and influence stock price movements. Institutional investors often conduct thorough research and have significant resources, making their investments a reliable indicator of a company's potential.