Following the first observation of an astrophysical high-energy neutrino flux with the IceCube observatory in 2013, planning for a next-generation neutrino telescope at the South Pole, IceCube-Gen2, is under way, which will significantly expand the sensitivity both towards high and low neutrino energies. The detector is envisioned to instrument $5 - 10\,\mathrm{km}^3$ of the deep clear ice with up to $10\,000$ optical modules to detect the Cherenkov light from charged secondaries created in the interaction of neutrinos in the ice. Apart from the larger volume, a significant increase in the sensitivity is expected to originate from advanced optical modules with several concepts currently being under development. One such concept is the multi-PMT Digital Optical Module (mDOM) which, in contrast to the "conventional" layout with a single ten-inch photomultiplier tube (PMT), features 24 three-inch PMTs inside a pressure vessel pointing isotropically in all directions. This layout provides an almost uniform angular acceptance and an increased effective area by more than a factor two. Additionally, directional information on the detected photons is obtained and background can be suppressed using local coincidences while at the same time the dynamic range of the module is increased.

The contribution provides an introduction to the design as well as an overview of the current status of mDOM development and prototype construction. It also highlights further optimization potential and remaining challenges en route to a fully functional multi-PMT optical module for IceCube-Gen2.