Sierra Oncology : Corporate Presentation June 2021

Corporate Presentation

June 2021

NASDAQ: SRRA

S A F E H A R B O R S TAT E M E N T

Except for statements of historical fact, any information contained in this presentation may be a forward-looking statement that reflects the Company's current views about future events and are subject to risks, uncertainties, assumptions and changes in circumstances that may cause events or the Company's actual activities or results to differ significantly from those expressed in any forward-looking statement. In some cases, you can identify forward- looking statements by terminology such as "may", "will", "should", "plan", "predict", "expect," "estimate," "anticipate," "intend," "goal," "strategy," "believe," and similar expressions and variations thereof. Forward-looking statements may include statements regarding the Company's business strategy, cash flows and funding status, potential growth opportunities, preclinical and clinical development activities, the timing and results of preclinical research, clinical trials and potential regulatory approval and commercialization of product candidates. Although the Company believes that the expectations reflected in such forward-looking statements are reasonable, the Company cannot guarantee future events, results, actions, levels of activity, performance or achievements. These forward-looking statements are subject to a number of risks, uncertainties and assumptions, including those described under the heading "Risk Factors" in documents the Company has filed with the SEC. These forward-looking statements speak only as of the date of this presentation and the Company undertakes no obligation to revise or update any forward- looking statements to reflect events or circumstances after the date hereof.

Certain information contained in this presentation may be derived from information provided by industry sources. The Company believes such information is accurate and that the sources from which it has been obtained are reliable. However, the Company cannot guarantee the accuracy of, and has not independently verified, such information.

T R A D E M A R K S :

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Sierra Oncology Highlights

Momelotinib (MMB) a potential cornerstone myelofibrosis therapy

JAK1 JAK2

ACVR1

Pivotal Phase 3 data expected Q1 2022

Robust data set on >820 myelofibrosis patients, some of whom have been treated for >10 years

Global commercial opportunity; JAK inhibitors approved for MF generate > $2 Billion annually

Experienced management team across Development, Regulatory & Commercial

$108 million in cash/equivalents as of 3/31/21

Focused on commercializing in North America

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Myelofibrosis Overview

Myelofibrosis (MF): a bone marrow cancer

• Caused by constitutive activation of JAK-STAT signaling
• Inflammation and fibrosis impair red blood cell production

Common manifestations of disease include constitutional symptoms, enlarged spleen and progressive anemia

Current treatments: JAK inhibitors are the mainstay option for intermediate and high-risk patients

Dysregulated JAK Signaling

Cell Wall

Cytoplasm

JAK1		JAK2	JAK2		JAK2
STAT		P	STAT		P

Inflammation	Fibrosis &
	Extramedullary
	Hematopoiesis
	Elevated Hepcidin

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Myelofibrosis: Global Market Overview

Rare oncology condition with ~40k diagnosed patients worldwide

• Median Age at Diagnosis: 60-67 years
• Median Survival for Intermediate / High-risk Patients: 2-7 years

Hematologist-oncologists(Hem-Oncs) are the primary disease manager

• 60-70%of patients treated by community physicians
• Referrals to academic centers driven by availability of SCT and clinical trials

• Hem-Oncs are reachable with a small sales force

FDA approved JAK inhibitors for myelofibrosis-ruxolitinib and fedratinib- with ruxolitinib reaching >$2.0 Billion in annual revenues globally

Approved JAK inhibitors address spleen and symptoms, but can worsen anemia

• JAKi treatment leads to myelosuppression
• Dose reductions are common, leading to loss of activity
• Some patients never receive JAKi due to hemoglobin and platelet count

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