G1 Therapeutics : May 2024 Corporate Presentation

Developing and Delivering Next Generation Therapies that Improve the Lives of People Living with Cancer

May 2024

Forward-Looking Statements

This presentation contains forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995. Words such as "may," "will," "expect," "plan," "anticipate," "estimate," "intend," "could," "believe," "goal," "projections," "indicate," "potential," "opportunity," and similar expressions (as well as other words or expressions referencing future events, conditions or circumstances) are intended to identify forward-looking statements. Forward-looking statements in this presentation include, but are not limited to, those relating to expectations for the commercial success of COSELA® (trilaciclib), our ability to further develop and expand the use of COSELA in the treatment of extensive-stage small cell lung cancer, the therapeutic potential of trilaciclib in the treatment triple-negative breast cancer ("TNBC") and with ADCs, that trilaciclib's greatest effect is on longer term endpoints including overall survival ("OS"), that trilaciclib may improve long-term immune surveillance for additional benefit after treatment, the expectation that achievement of the OS endpoint in the ongoing PRESERVE 2 Phase 3 clinical trial is expected to enable global regulatory submissions in 2024 and beyond, that G1's cash runway is expected to extend into the third quarter of 2025, global expansion, and that achieving the OS primary endpoint in the Phase 3 TNBC trial may serve as a catalyst for global expansion plans. In addition, COSELA may not achieve the degree of market acceptance for commercial success, the potential to demonstrate trilaciclib + gem/carbo as 1L TNBC standard of care, and the impact of pandemics such as COVID-19 (coronavirus), are based on our expectations and assumptions as of the date of this presentation. Each of these forward-looking statements involves risks and uncertainties that may cause our actual results to materially differ from those expressed or implied in such statements. Investors, potential investors, and others should give careful consideration to these risks and uncertainties. Applicable risks and uncertainties are discussed in our filings with the U.S. Securities and Exchange Commission, including the "Risk Factors" sections contained therein and include, but are not limited to, our ability to successfully commercialize COSELA; the dependence on the commercial success of COSELA; our ability to complete clinical trials for, obtain approvals for, and commercialize additional indications of COSELA and any of our product candidates other than COSELA; our initial success in clinical trials may not be indicative of results obtained when these trials are completed or in later stage trials; the inherent uncertainties associated with developing new products or technologies and operating as a commercial-stage company; chemotherapy shortages and market conditions. Except as required by law, we assume no obligation to update any forward-looking statements contained herein to reflect any change in expectations, even as new information becomes available.

G1Therapeutics® and G1Therapeutics logo and COSELA® and COSELA logo are trademarks of G1 Therapeutics, Inc. ©2024 G1 Therapeutics, Inc.

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G1 Therapeutics: Opportunities for Significant Growth

Unique Marketed Product in	• Novel product that provides meaningful patient benefits via transient G1 arrest of HSPCs and T-Cells
U.S. with Growing Revenue	• Established U.S. commercial infrastructure with growing revenue in initial ES-SCLC indication
Potential to Transform	• Late 2Q24 (est.) Phase 3 final readout would provide important potential global commercial opportunity
1L TNBC Treatment	• Robust OS observed in randomized Phase 2 with improvement continuing with subsequent therapies
Opportunity to Improve Safety	• Phase 2 with sacituzumab govitecan serves as proof-of-concept for trilaciclib in TROP2 ADC combinations
and Efficacy of Leading ADCs	• Following compelling initial results in January, mature efficacy results to be presented at ASCO 2024
Positioned for Global	• Evaluating additional late-stage studies and conducting research into next generation products
• Planning to secure a partner for global expansion on a successful 1L TNBC readout
Expansion and Future Growth
	• Anticipated cash runway into 3Q 2025

Note: HSPCs: Hematopoietic stem and progenitor cells, ES-SCLC: Extensive Stage Small Cell Lung Cancer, 1L: First line, TNBC: Triple negative breast cancer; OS: overall survival, ADC: antibody-drug conjugate,

ASCO: American Association of Clinical Oncology

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Agenda

Unique Marketed Product in U.S. with Growing Revenue

Potential to Transform 1L TNBC Treatment

Opportunity to Improve Safety and Efficacy of Leading ADCs

Positioned for Global Expansion and Future Growth

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Trilaciclib Mechanism of Action

Temporarily Blocks Progression through Cell Cycle Via Transient CDK4/6 Inhibition

M

G2 HSPCs

Myeloid Lineages

Lymphoid Lineages G1

S	Transiently arrests HSPCs
and T cells in G1 Phase

Potential Benefits

Protects Bone Marrow and Immune System from	Improves Long-Term Immune Surveillance
Cytotoxic Damage During Treatment	for Additional Benefit After Treatment

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Unique Product Attributes for Robust Transient G1 Arrest

Critical Characteristics of Trilaciclib Enabling Robust Transient G1 Arrest

IV administration

Precisely timed effect through

rapid IV onset

Potent and selective

CDK4 and CDK6 inhibition

Robust G1 arrest through

targeted activity

Short half-life

Optimizes ability for T-cells

to proliferate

These attributes are critical to maximize the benefits of transient CDK4/6 inhibition

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Potential for Strong Growth within U.S. ES-SCLC Market

~20K ES-SCLC Patients in U.S. Receive Indicated Chemotherapy	Satisfaction with COSELA® (trilaciclib)4
		100%				4%
						5%				14%
		75%
	High satisfaction among active	50%
~13% Market	prescribers driven by fewer			91%				86%
Penetration2	hospitalizations and protection of
	multiple cell lineages3	25%
$700M+ Market		0%
Opportunity1					% of Oncologists		% of NP/PAs
					Very Satisfied /		Neutral		Very Dissatisfied /
					Satisfied		Dissatisfied

Meaningful opportunity to continue growing share in $700M+ U.S. ES-SCLC market,

with high levels of satisfaction expressed by existing prescribers

1. Based on ~20k patients and $36,600 current WAC pricing for 24 vials of trilaciclib (assumed 4 cycles per patient based on standard 1L ES-SCLC chemotherapy regimens)
2. 1L market penetration as of 1Q 2024
3. According to active prescriber data from internal ATU Tracking Studies, Q3 2023, which is further supported by Real World Evidence

4. Prescriber data from internal ATU Tracking Studies, Q3 2023

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Strong COSELA Growth Expected in 2024

1Q24 Highlights

• $14.1M in net COSELA sales
• 4% quarterly vial volume growth; 33% growth over 1Q23
• Localized/regional variability masked strong execution and growth
• • 30% growth in West region
  • 20% growth in customers covered by Strategic accounts
• Enhanced and added new contracted customers
• Added three new top 100 accounts through April (78 total)
• 63 top 100 accounts ordered during quarter; highest since launch

April 2024 Highlights

• Highest volume & ex factory sales month since launch
• ~30% growth by large customers with slow start to 1Q24
• Double digit growth in contracted customers

Sales trends support confidence in COSELA net sales guidance of $60M to $70M

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Potential for Future Development and Expansion in ES-SCLC

Expected Future Data in ES-SCLC

	Lurbinectedin	Topotecan	Real World
	Combination	Combination Post-
	Evidence
	(Phase 2)	Marketing Study
Setting	2L ES-SCLC	2L ES-SCLC	1L/2L ES-SCLC
Combination	Lurbinectedin	Topotecan	Chemotherapy
Target	~30 Patients	~300 Patients	NA
Enrollment
	Evaluating	Evaluating overall	Evaluating OS
Details	myeloprotection	from U.S.
survival ("OS")
	and efficacy	Claims data
Sponsor	UNC	G1	G1
Lineberger

Ongoing clinical studies and real-world-evidence will help guide

future development and expansion efforts in ES-SCLC

1. Huan et al., Assessment of Hospitalizations and Cytopenia Events Among Patients with Extensive Stage Small Cell Lung Cancer (ES-SCLC) Receiving Chemotherapy with Trilaciclib; ASCO Quality Care Symposium, October 2023, Abstract 531

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Agenda

Unique Marketed Product in U.S. with Growing Revenue

Potential to Transform 1L TNBC Treatment

Opportunity to Improve Safety and Efficacy of Leading ADCs

Positioned for Global Expansion and Future Growth

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