A trial hold (of any sort) is placed by regulators. They are based on safety/ethics.
It seems as though you are wrong again Ex...No safety/ethics issues cited in this recent example and ironically looks very similar to NWBO. Partial Halt on new patient recruitment and then the halt is lifted. Absolutely zero to due with safety/ethics.
The U.S. Food and Drug Administration (FDA) placed Princeton, NJ-based Advaxis’ Phase III clinical trial of axalimogene filolisbac (AXAL) in advanced cervical cancer on partial clinical hold. No safety issues were cited. Instead, it appears related to the company’s proposal to modify the trial’s analysis plan and various chemistry, manufacturing and controls (CMC) issues. The trial is an ongoing randomized, double-blinded, placebo-controlled, pivotal trial of AXAL in high-risk, locally advanced cervical cancer (AIM2CERV). The partial hold means no new patients can enroll in the trial until the hold is lifted. https://www.biospace.com/article/fda-places-advaxis-cervical-cancer-trial-on-clinical-hold/