EXHIBIT 99

FORM 4 JOINT FILER INFORMATION

Names of Joint Filers:

Canaan X L.P.

Canaan Partners X LLC

Address of Joint Filers:

c/o Canaan Partners

285 Riverside Avenue, Suite 250

Westport, CT 06880

Designated Filer:

Canaan X L.P.

Issuer and Ticker Symbol:

IDEAYA Biosciences, Inc. [IDYA]

Date of Event:

May 28, 2019

Signatures of Joint Filers:

Canaan X L.P.

  By: Canaan Partners X LLC, its General Partner

By: /s/ Janine MacDonald       Attorney-in-Fact

Canaan Partners X LLC

By: /s/ Janine MacDonald       Attorney-in-Fact

ACTIVE/99703234.2