Well, against the radiation from cancer treatment at least. And it appears to inhibit tumor growth:

One in vitro study using the HO-8910 (human ovarian cancer) cell line noted that treatment with an acidic polysaccharide derived from the roots appeared to reduce the invasion and migration potential of the tumor cell while suppressing proliferation; thought to be through a reduction in CD44 expression, a cellular adhesion molecule that had its expression (as a percentage of total cells) decreased dose-dependently in response to the acidic polysaccharide.[9] Cell survival after 48 hour incubation reached 81.72% of baseline at 25ug/mL, and appeared to reach 39.35% at 200ug/mL, suggestive of apoptotic capabilities as well.[9] Inhibition of tumor growth has been noted in mice injected with tumor cells in response to oral administration of 50 or 100mg/kg of one of two polysaccharides in the range of 22.86-56.73% inhibition; the active control of cyclophosphamide at 30mg/kg injected achieved 63.67% inhibition.[20]

https://examine.com/supplements/codonopsis-pilosula/