ZYME IPO has rare partial exercise of underwriter’s option: https://finance.yahoo.com/news/zymeworks-announces-partial-exercise-over-115900269.html At the 5/3/17 IPO, 4.5M shares were issued @$13.00 (https://finance.yahoo.com/news/zymeworks-announces-closing-initial-public-131600990.html ), but only 58% of the shares in the 675K-share underwriter’s option were exercised. Looking at the price history, it’s pretty clear that the underwriter was (legally) supporting the stock at the IPO price, but they eventually gave up.