POWER OF ATTORNEY

KNOW ALL MEN BY THESE PRESENTS, that each person whose signature
appears below hereby constitutes and appoints Mark McDonnell his true and
lawful attorney-in-fact, with full power of substitution, to sign any and
all instruments, certificates and documents that may be necessary, desirable
or appropriate to be executed on behalf of himself as an individual or in
his capacity as a direct or indirect general partner, director, officer or
manager of any partnership, corporation or limited liability company, pursuant
to section 13 or 16 of the Securities Exchange Act of 1934, as amended (the
"Exchange Act"), and any and all regulations promulgated thereunder, and to
file the same, with all exhibits thereto, and any other documents in connection
therewith, with the Securities and Exchange Commission, and with any other
entity when and if such is mandated by the Exchange Act or by the Financial
Industry Regulatory Authority, granting unto said attorney-in-fact full power
and authority to do and perform each and every act and thing necessary,
desirable or appropriate, fully to all intents and purposes as he might or could
do in person, thereby ratifying and confirming all that said attorney-in-fact,
or his substitutes, may lawfully do or cause to be done by virtue hereof.

IN WITNESS WHEREOF, this Power of Attorney has been signed as of the
26th day of July, 2017.

ARCH VENTURE FUND VIII OVERAGE, L.P.

By: ARCH Venture Partners VIII, LLC
its General Partner

By: /s/ Keith Crandell
Managing Director

ARCH VENTURE PARTNERS VIII, L.P.

By:  ARCH Venture Partners VIII, LLC
its General Partner

By: /s/ Keith Crandell
Managing Director