100,000 Shares ESSA Pharma Inc.

UNDERWRITING AGREEMENT

As Representative of the several Underwriters

New York, New York 10022

Ladies and Gentlemen:

Introductory. ESSA Pharma Inc., a

company incorporated under the laws of the Province of British Columbia (the "Company"), proposes to issue and

sell to the several underwriters named in Schedule A (the "Underwriters") an aggregate of 7,100,000 of

its common shares, without par value (the "Shares"). The 7,100,000 Shares to be sold by the Company are called

the "Firm Shares." In addition, the Company has granted to the Underwriters an option to purchase up to an additional

1,065,000 Shares as provided in Section 2. The additional 1,065,000 Shares to be sold by the Company pursuant to such option are

collectively called the "Optional Shares." The Firm Shares and, if and to the extent such option is exercised,

the Optional Shares are collectively called the "Offered Shares." Jefferies LLC ("Jefferies")

has agreed to act as representative of the several Underwriters (in such capacity, the "Representative") in

connection with the offering and sale of the Offered Shares. To the extent there are no additional underwriters listed on Schedule

A, the term "Representative" as used herein shall mean you, as Underwriter, and the term "Underwriters"

shall mean either the singular or the plural, as the context requires.

The Company has prepared and filed with

the Securities and Exchange Commission (the "Commission") a shelf registration statement on Form F-3, File

No. 333-225969, including a base prospectus (the "Base Prospectus") to be used in connection with the public

offering and sale of the Offered Shares. Such registration statement, as amended, including the financial statements, exhibits

and schedules thereto, in the form in which it became effective under the United States Securities Act of 1933, as amended, and

the rules and regulations promulgated thereunder (collectively, the "Securities Act"), including all documents

incorporated or deemed to be incorporated by reference therein and any information deemed to be a part thereof at the time of effectiveness

pursuant to Rule 430A or 430B under the Securities Act, is called the "Registration Statement." Any registration

statement filed by the Company pursuant to Rule 462(b) under the Securities Act in connection with the offer and sale of the Offered

Shares is called the "Rule 462(b) Registration Statement," and from and after the date and time of filing of

any such Rule 462(b) Registration Statement the term "Registration Statement" shall include the Rule 462(b) Registration

Statement. The preliminary prospectus supplement dated July 28, 2020 describing the Offered Shares and the offering thereof (the

"Preliminary Prospectus Supplement"), together with the Base Prospectus, is called the "Preliminary

Prospectus," and the Preliminary Prospectus and any other prospectus supplement to the Base Prospectus in preliminary

form that describes the Offered Shares and the offering thereof and is used prior to the filing of the Prospectus (as defined below),

together with the Base Prospectus, is called a "preliminary prospectus." As used herein, the term "Prospectus"

shall mean the final prospectus supplement to the Base Prospectus that describes the Offered Shares and the offering thereof (the

"Final Prospectus Supplement"), together with the Base Prospectus, in the form first used by the Underwriters

to confirm sales of the Offered Shares or in the form first made available to the Underwriters by the Company to meet requests

of purchasers pursuant to Rule 173 under the Securities Act. References herein to the Preliminary Prospectus, any preliminary prospectus

and the Prospectus shall refer to both the prospectus supplement and the Base Prospectus components of such prospectus. As used

herein, "Applicable Time" is 8:00 p.m. (New York City time) on July 28, 2020. As used herein, "free

writing prospectus" has the meaning set forth in Rule 405 under the Securities Act, and "Time of Sale Prospectus"

means the Preliminary Prospectus, as amended or supplemented immediately prior to the Applicable Time, together with the free writing

prospectuses, if any, identified in Schedule B hereto. As used herein, "Road Show" means a "road

show" (as defined in Rule 433 under the Securities Act) relating to the offering of the Offered Shares contemplated hereby

that is a "written communication" (as defined in Rule 405 under the Securities Act).

The Company has also prepared and filed

with the securities regulatory authorities (the "Canadian Qualifying Authorities") in each of the provinces

of British Columbia, Alberta and Ontario (the "Canadian Qualifying Jurisdictions") a preliminary short form

base shelf prospectus dated June 28, 2018 (the "Canadian Preliminary Base Prospectus"), and the Canadian Base

Prospectus (as defined below), to be used in connection with the public offering and sale of the Offered Shares. The British Columbia

Securities Commission (the "BCSC") is the Company's principal regulator under the passport system procedures

provided for under Multilateral Instrument 11-102 - Passport System and National Policy 11-202 - Process

for Prospectus Reviews in Multiple Jurisdictions (collectively, the "Passport System") in respect of any

securities offerings pursuant to the Canadian Base Prospectus. The BCSC has issued a receipt, which is deemed to also be a receipt

of the Alberta Securities Commission and evidences the receipt of the Ontario Securities Commission pursuant to the Passport System

(a "Passport Decision Document"), for each of the Canadian Preliminary Base Prospectus and the Canadian Base

Prospectus. The term "Canadian Base Prospectus" means the final short form base shelf prospectus dated July

12, 2018 of the Company, including any documents incorporated by reference therein and the documents otherwise deemed to be incorporated

by reference therein pursuant to Canadian Securities Laws (as defined below), at the time the BCSC issued a Passport Decision Document

with respect thereto in accordance with Canadian Securities Laws, including National Instrument 44-101 - Short Form Prospectus

Distributions ("NI 44-101") and National Instrument 44-102 - Shelf Distributions (together,

the "Canadian Shelf Procedures"). The Company has also prepared and filed with the Qualifying Authorities in

accordance with the Canadian Shelf Procedures a preliminary prospectus supplement dated July 28, 2020 relating to the Offered Shares,

which excluded certain information (the "Canadian Preliminary Prospectus Supplement" and, together with the

Canadian Base Prospectus, and including any documents incorporated therein by reference and the documents otherwise deemed to be

incorporated by reference therein pursuant to Canadian Securities Laws, the "Canadian Preliminary Prospectus").

In addition, the Company shall prepare and

file with the Canadian Qualifying Authorities a final prospectus supplement (the "Canadian Final Prospectus Supplement")

to the Canadian Base Prospectus relating to the Offered Shares, which shall include the information omitted from the Canadian Preliminary

Prospectus and otherwise supersedes the Canadian Preliminary Prospectus in its entirety (together with the Canadian Base Prospectus,

and including any documents incorporated therein by reference and the documents otherwise deemed to be a part thereof or included

therein pursuant to Canadian Securities Laws, the "Canadian Prospectus").

All references in this Agreement to the

Registration Statement, the Preliminary Prospectus, the Canadian Preliminary Prospectus, any preliminary prospectus, the Base Prospectus,

the Canadian Base Prospectus, the Prospectus and the Canadian Prospectus shall include the documents incorporated or deemed to

be incorporated by reference therein. All references in this Agreement to financial statements and schedules and other information

which are "contained," "included" or "stated" in, or "part of" the Registration

Statement, the Rule 462(b) Registration Statement, the Preliminary Prospectus, the Canadian Preliminary Prospectus, any preliminary

prospectus, the Base Prospectus, the Canadian Base Prospectus, the Time of Sale Prospectus, the Prospectus or the Canadian Prospectus,

and all other references of like import, shall be deemed to mean and include all such financial statements and schedules and other

information which is or is deemed to be incorporated by reference in the Registration Statement, the Rule 462(b) Registration Statement,

the Preliminary Prospectus, the Canadian Preliminary Prospectus, any preliminary prospectus, the Base Prospectus, the Canadian

Base Prospectus, the Time of Sale Prospectus, the Prospectus or the Canadian Prospectus, as the case may be. All references in

this Agreement to amendments or supplements to the Registration Statement, the Preliminary Prospectus, any preliminary prospectus,

the Base Prospectus, the Time of Sale Prospectus or the Prospectus shall be deemed to mean and include the filing of any document

under the United States Securities Exchange Act of 1934, as amended, and the rules and regulations promulgated thereunder (collectively,

the "Exchange Act") that is or is deemed to be incorporated by reference in the Registration Statement, the

Preliminary Prospectus, any preliminary prospectus, the Base Prospectus, or the Prospectus, as the case may be. All references

in this Agreement to (i) the Registration Statement, the Preliminary Prospectus, any preliminary prospectus, the Base Prospectus

or the Prospectus, any amendments or supplements to any of the foregoing, or any free writing prospectus, shall include any copy

thereof filed with the Commission pursuant to its Electronic Data Gathering, Analysis and Retrieval System ("EDGAR")

and (ii) the Prospectus shall be deemed to include any "electronic Prospectus" provided for use in connection

with the offering of the Offered Shares as contemplated by Section 3(n) of this Agreement. All references in this Agreement to

the Canadian Preliminary Prospectus, the Canadian Base Prospectus, the Canadian Prospectus, or any amendment or supplement to any

of the foregoing, shall include the copy filed with the Canadian Qualifying Authorities pursuant to the System for Electronic Document

Analysis and Retrieval ("SEDAR").

In the event that the Company has only one

subsidiary, then all references herein to "subsidiaries" of the Company shall be deemed to refer to such single subsidiary,

The Company hereby confirms its agreements

with the Underwriters as follows:

Representations and Warranties of the Company. The Company hereby represents, warrants and covenants to each Underwriter,

as of the date of this Agreement, as of the First Closing Date (as hereinafter defined) and as of each Option Closing Date (as