X0306 4 2019-07-15 0 0001709401 Rubius Therapeutics, Inc. RUBY 0001239757 LANGER ROBERT C/O RUBIUS THERAPEUTICS, INC. 399 BINNEY STREET, SUITE 300 CAMBRIDGE MA 02139 1 0 0 0 Common Stock 2019-07-15 4 M 0 7500 0.15 A 7500 D Common Stock 2019-07-15 4 S 0 7500 14.9398 D 0 D Stock Option (Right to Buy) 0.15 2019-07-15 4 M 0 7500 0 D 2025-02-04 Common Stock 7500 127500 D The sale was effected pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $14.70 to $15.42, inclusive. The reporting person undertakes to provide to Rubius Therapeutics, Inc., any security holder of Rubius Therapeutics, Inc., or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the ranges set forth in this footnote. 25% of this option shall vest on December 5, 2015, then in 12 equal quarterly installments thereafter. /s/ Joanne M. Protano, Attorney-in-Fact 2019-07-17