The selling securityholders and any underwriters, broker-dealers, or agents that participate
in the sale of Securities or interests therein may be underwriters within the meaning of Section 2(11) of the Securities Act. Any discounts, commissions, concessions, or profit they earn on any resale of such securities may be
underwriting discounts and commissions under the Securities Act. If any selling securityholder is an underwriter within the meaning of Section 2(11) of the Securities Act, then the selling securityholder will be subject to the
prospectus delivery requirements of the Securities Act. Underwriters and their controlling persons, dealers, and agents may be entitled, under agreements entered into with us and the selling securityholders, to indemnification against and
contribution toward specific civil liabilities, including liabilities under the Securities Act.
To the extent required, the number of
Securities to be sold, the respective purchase prices and public offering prices, the names of any agent, dealer, or underwriter, and any applicable discounts, commissions, concessions, or other compensation with respect to a particular offer will
be set forth in an accompanying prospectus supplement or, if appropriate, a post-effective amendment to the registration statement that includes this prospectus.
To facilitate the offering of securities offered by the selling securityholders, certain persons participating in the offering may engage in
transactions that stabilize, maintain, or otherwise affect the price of our Securities. This may include over-allotments or short sales, which involve the sale by persons participating in the offering of more Securities than were sold to them. In
these circumstances, these persons would cover such over-allotments or short positions by making purchases in the open market or by exercising their over-allotment option, if any. In addition, these persons may stabilize or maintain the price of our
Securities by bidding for or purchasing Securities in the open market or by imposing penalty bids, whereby selling concessions allowed to dealers participating in the offering may be reclaimed if Securities sold by them are repurchased in connection
with stabilization transactions. The effect of these transactions may be to stabilize or maintain the market price of our Securities at a level above that which might otherwise prevail in the open market. These transactions may be discontinued at
any time.
Under the registration rights agreement by and among the Company, Syncona Portfolio Limited (Syncona) and certain
other shareholders of the Company, dated as of June 26, 2018 (the Registration Rights Agreement), we have agreed to indemnify the selling securityholders party thereto against certain liabilities that they may incur in connection
with the sale of the securities registered hereunder, including liabilities under the Securities Act, and to contribute to payments that the selling securityholders may be required to make with respect thereto. In addition, we and the selling
securityholders may agree to indemnify any underwriter, broker-dealer, or agent against certain liabilities related to the selling of the securities, including liabilities arising under the Securities Act.
We have agreed to maintain the effectiveness of the registration statement of which this prospectus forms a part until all such securities
have been sold under such registration statement or under Rule 144 under the Securities Act or are no longer outstanding, or under other circumstances as described in the Registration Rights Agreement. We have agreed to pay all expenses in
connection with this offering, other than underwriting fees, discounts, selling commissions, stock transfer taxes, and certain legal expenses. The selling securityholders will pay, on a pro rata basis, any underwriting fees, discounts, selling
commissions, stock transfer taxes, and certain legal expenses relating to the offering.
The selling securityholders may use this
prospectus in connection with resales of Securities. This prospectus and any accompanying prospectus supplement will identify the selling securityholders, the terms of our Securities, and any material relationships between us and the selling
securityholders. The selling securityholders may be deemed to be underwriters under the Securities Act in connection with Securities they resell and any profits on the sales may be deemed to be underwriting discounts and commissions under the
Securities Act. Unless otherwise set forth in a prospectus supplement, the selling securityholders will receive all the net proceeds from the resale of Securities.
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