Why Are Mersana Therapeutics Shares Trading Lower On Friday?

Mersana Therapeutics Inc MRSN stock is moving lower during the market trading session. Investors are reacting to interim data from the ovarian cancer Phase 1 trial evaluating Upifitamab Rilsodotin (UpRi, previously XMT-1536).
See the related Company presentation here.
Complete response was observed in 2 patients with platinum-resistant ovarian cancer at the lower dose. A confirmed objective response rate (ORR) of 34% and disease control rate (DCR) of 87% in NaPi2b high population was observed.
Interim data showed that 67% of patients (n=73 evaluable patients) had reductions in target tumor lesions.
Notably, a heavily pre-treated patient with BRCA1/2 negative high-grade serous ovarian cancer received nine cycles of UpRi at a lower dose of 36 mg/m2.
The patient achieved a confirmed partial response (PR) with almost 41.4% tumor reduction.
Mersana said similar efficacy was observed across the three dose levels, with a trend toward higher efficacy with a lower dose.
Mersana plans to take 36 mg/m2 up to a maximum of ~80 mg dose strength forward further evaluation.
Related Content: Mersana Starts UpRi Dosing In Heavily Pretreated Cohort Of Ovarian Cancer Patients.
Price Action: MRSN stock is down 35.7% at $9.04 during the market session on the last check Friday.