With his ideas still informant, Albert Einstein was 22 years old when he sat out alone on foot across the Alps.
It is a regular formation from the primary meaning of
Inform: I, 2. (obelised as obsolete) intransitive to take shape; to form. -1652 (Shorter Oxford)
The -ant ending is a present participle. Therefore
Informant adj. taking shape. -2015(?) (obsolete?)
Equally it is properly formed, & accurately derived from the Latin: (Ainsworth, Thesaurus; who gives a quotation from Cicero to justify (2))
Informo -are, act. (1) to form, shape, or fashion. (2) to contrive or design in the mind.