Checkpoint inhibitors may target one or two different proteins, but cancer cells can upregulate many. Also, they are given systemically, which increases cost and toxicities. Back some years ago, SNY acquired Kiadis, a company working on off-the-shelf (healthy donor derived) NK cell therapies [1]. Fast forward, and they are presenting a number of posters at the AACR conference next month. One of these is looking at NKs with four inhibitory receptors found on them knocked out alone or in combination (using CRISPR), with one being KIR2DL5, as shown in the link you provided.

Knockout of each enhanced NK cell killing compared to wildtype NK cells. Double, triple or quadruple knockout of these receptors resulted in further increased killing of cancer cells.

Ref:
1 https://www.globenewswire.com/news-release/2020/11/02/2118122/0/en/Sanofi-offers-to-acquire-Kiadis-a-clinic
al-stage-company-developing-cell-based-immunotherapy-products.html