Net loss per share attributable to common stockholders - Schedule of antidilutive securities excluded from computation of earnings per share (Detail) - shares	9 Months Ended
	Oct. 31, 2020	Oct. 31, 2019
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	5,905,279	6,873,284
Stock options to purchase common stock and restricted stock units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	5,830,142	6,645,106
Warrants to purchase common stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	75,137	228,178