A Study of NI-1801 in Patients with Mesothelin Expressing Solid Cancers

Treatment will be administered in 28-day cycles for up to 12 months until disease progression, unacceptable toxicity, or Investigator/patient decision to withdraw study consent. Each subject will receive the assigned dose of NI-1801 on Cycle 1, Day 1. Subsequent doses will be given Q2W, which may be adjusted to every three weeks if recommended from the ongoing PK/PD model analysis.

In the combination with pembrolizumab cohort, the starting NI-1801 dose will be 300 mg. Pembrolizumab will be administered at the dosage of 400 mg every 6 weeks, in 4 cycles. Pembrolizumab will be administered as first drug; later, NI-1801 will be infused after 30 minutes.

The experimental arm will receive the investigational drug NI-1801 at the P2RD every two weeks in combination with weekly administration of paclitaxel (80 mg/m\^2) over 4-week cycles. The control arm will be treated with weekly paclitaxel at the same regimen.

The control arm will be treated with weekly administration of paclitaxel (80 mg/m\^2) over 4-week cycles.