INEFFICACY
inefficacy, inefficaciousness
(noun) a lack of efficacy
Source: WordNet® 3.1
Etymology
Noun
inefficacy (usually uncountable, plural inefficacies)
The condition of being ineffective
Source: Wiktionary
In*ef"fi*ca*cy, n. Etym: [L. inefficacia. See In- not, and Efficacy.]
Definition: Want of power to produce the desired or proper effect;
inefficiency; ineffectualness; futility; uselessness; fruitlessness;
as, the inefficacy of medicines or means.
The seeming inefficacy of censures. Bp. Hall.
The inefficacy was soon proved, like that of many similar medicines.
James Gregory.
Source: Webster’s Unabridged Dictionary 1913 Edition