Summit Therapeutics Reports Financial Results and Operational Progress for the Second Quarter and Six Months Ended

Summit Therapeutics Reports Financial Results

and Operational Progress

for the Second Quarter and Six Months Ended

Cambridge, Massachusetts, August 11, 2021 -

Summit Therapeutics Inc. (NASDAQ: SMMT) ("Summit," "we," or the "Company") today reports its financial results

and provides an update on its operational progress for the second quarter and six months ended June 30, 2021.

Note: A glossary of terms is included at the

end of this document in order to allow for the ease of understanding of terms or concepts used throughout this release.

Financial Highlights

Ridinilazole for C. difficile Infection

In conjunction with this release, we have simultaneously

issued a press release today providing an update with respect to our Phase III Ri-CoDIFy clinical trials. Please refer to that release

for our current operational progress with respect to ridinilazole.

SMT-738 for Carbapenem-Resistant Enterobacteriaceae

The DDS-04 compound series is a novel class of

precision antibiotics generated from our Discuva Platform with a new mechanism of action that acts via the novel bacterial target, LolCDE.

SMT-738 is the first molecule of this novel class with the potential to treat multidrug resistant infections caused by a large family

of pathogenic Gram-negative bacteria, the Enterobacteriaceae, that include serious human pathogens such as Escherichia coli and

Klebsiella pneumoniae. Combining a novel antibiotic class (SMT-738) with a clinically unexploited target (LolCDE) mitigates the

risk of pre-existing resistance, potentially allowing for the effective treatment of Enterobacteriaceae-caused infections that currently

have very limited and failing treatment options due to resistance to existing antibiotic classes.

Corporate Highlights

About C. difficile Infection

Clostridioides difficile, or C. difficile,

infection (CDI) is a bacterial infection of the colon that produces toxins causing inflammation of the colon, severe watery diarrhea,

painful abdominal cramping, nausea, fever, and dehydration. CDI can also result in more serious disease complications, including bowel

perforation, sepsis, and death. CDI is a contagious infectious disease that represents a serious healthcare issue in hospitals, long-term

care facilities, and the wider community. Summit estimates that there are approximately 500,000 cases of CDI each year across the United

States with acute care costs exceeding $5.4 billion in the US based on a meta-analysis published in the Journal of Global Health,

About Enterobacteriaceae

Enterobacteriaceae are a family of bacteria

responsible for serious infections across a number of conditions including bloodstream infections, urinary tract infections, and

hospital-acquired pneumonias. Multidrug resistant Enterobacteriaceae are resistant to treatment by most or occasionally all existing

antibiotics. The most difficult to treat among them are the carbapenem-resistant Enterobacteriaceae (CRE), which are classified as

an Urgent Threat by the US Centers for Disease Control and Prevention (CDC).

About Summit Therapeutics

The overriding objective of Summit Therapeutics

is to create value for patients, hospital caregivers, and community-based healthcare providers, as well as healthcare payers around the

world. We seek to create value by developing drugs with high therapeutic efficacy - curing the cause of the patient's condition with minimal

or zero disease recurrence or antimicrobial resistance, for the longest extent possible - and minimizing the trauma caused to the patient

and healthcare ecosystem by minimizing serious side effects, disease recurrence, and inaccessibility to our treatments as a result of

financial or other barriers. Summit Therapeutics, empowered by its Discuva Platform, the Company's innovative antibiotic discovery

engine, and supported by BARDA and CARB-X funding, intends to be the leader in patient-friendly and paradigm-shifting treatments for infectious

diseases and other significant unmet medical needs while being an ally to physicians. Our new mechanism pipeline product candidates are

designed with the goal to become the patient-friendly, new-era standard of care, by working in harmony with the human microbiome to treat

prospective patients suffering from infectious diseases, initially focusing on Clostridioides difficile infection (CDI). Currently,

Summit's lead product candidate, ridinilazole, is a novel, first-in-class drug engaged in a global Phase III trial program versus

vancomycin, for use as first-line therapy for the treatment of initial and recurrent Clostridioides difficile infection, and to

show superiority in sustained clinical response. Commercialization of ridinilazole is subject to regulatory approvals. SMT-738, the second

candidate within Summit's portfolio, is currently in the IND-enabling phase for the treatment of multidrug resistant infections,

specifically those caused by carbapenem-resistant Enterobacteriaceae (CRE).

For more information, please visit https://www.summittxinc.com

Contact Summit Investor Relations:

Head of Investor Relations & Corporate Strategy

Summit Forward-looking Statements

Any statements in this press release about the

Company's future expectations, plans and prospects, including but not limited to, statements about the clinical and preclinical

development of the Company's product candidates, the therapeutic potential of the Company's product candidates, the potential

commercialization of the Company's product candidates, the timing of initiation, completion and availability of data from clinical

trials, the potential submission of applications for marketing approvals, the impact of the COVID-19 pandemic on the Company's

operations and clinical trials and other statements containing the words "anticipate," "believe," "continue,"

"could," "estimate," "expect," "intend," "may," "plan," "potential,"

"predict," "project," "should," "target," "would," and similar expressions, constitute

forward-looking statements within the meaning of The Private Securities Litigation Reform Act of 1995. Actual results may differ materially

from those indicated by such forward-looking statements as a result of various important factors, including: the uncertainties inherent

in the initiation of future clinical trials, availability and timing of data from ongoing and future clinical trials and the results

of such trials, global public health crises, including the coronavirus COVID-19 outbreak, that may affect timing and status of our clinical

trials and operations, whether preliminary results from a clinical trial will be predictive of the final results of that trial or whether

results of early clinical trials or preclinical studies will be indicative of the results of later clinical trials, expectations for

regulatory approvals, laws and regulations affecting government contracts and funding awards, availability of funding sufficient for

the Company's foreseeable and unforeseeable operating expenses and capital expenditure requirements and other factors discussed

in the "Risk Factors" section of filings that the Company makes with the Securities and Exchange Commission. Any change to

our ongoing trials could cause delays, affect our future expenses, and add uncertainty to our commercialization efforts, as well as to

affect the likelihood of the successful completion of clinical development of ridinilazole. Accordingly, readers should not place undue

reliance on forward-looking statements or information. In addition, any forward-looking statements included in this press release represent

the Company's views only as of the date of this release and should not be relied upon as representing the Company's views

as of any subsequent date. The Company specifically disclaims any obligation to update any forward-looking statements included in this

SUMMIT THERAPEUTICS, INC.

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS

AND COMPREHENSIVE LOSS

In thousands, except per share data

CONDENSED CONSOLIDATED BALANCE SHEET INFORMATION

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOW INFORMATION

Appendix: Glossary of Critical Terms

Antibiotic resistance genes -

Genes known to be involved in bacterial resistance; such genes may include for example beta-lactamases which can inactivate various beta-lactam

Bile acids - a collection of

steroid-based gut metabolites, the balance of the amount of and types of bile acids in the gut microbiome are believed to play an important

role in the development of or prevention of an initial and potential recurrent infection of Clostridioides difficile.i

Bloodstream infections - an

infectious disease defined by the presence of viable bacterial or fungal microorganisms in the bloodstream

that elicit or have elicited an inflammatory response.ii

Carbapenem-Resistant Enterobacteriaceae

(CRE) - Enterobacteriaceae that are resistant to carbapenems, a type of antibiotic used

to treat some of the most resistant forms of gram-negative bacteria. This resistance means that there are fewer options available