Syndax Pharmaceuticals : First Quarter 2024 Conference Call

First Quarter Financial Results Presentation / May 8, 2024

Forward-looking statements disclosure

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" and similar expressions (as well as other words or expressions referencing future events, progress, timing or circumstances) are intended to identify forward-looking statements. All statements other than statements of historical facts contained in this presentation, including statements regarding future operations, financial results and the financial condition of Syndax Pharmaceuticals, Inc. ("Syndax" or the "Company"), including financial position, strategy and plans, the progress, timing, clinical development and scope of clinical trials and the reporting of clinical data for Syndax's product candidates, the progress of regulatory submissions and approvals and subsequent commercialization and the potential use of Syndax's product candidates to treat various cancer indications and fibrotic diseases, and Syndax's expectations for liquidity and future operations, are forward-looking statements. Many factors may cause differences between current expectations and actual results, including unexpected safety or efficacy data observed during preclinical studies or clinical trials, clinical site activation rates or clinical trial enrollment rates that are lower than expected; changes in expected or existing competition; the impact of macroeconomic conditions (the Russia-Ukraine war, inflation, among others) on Syndax's business and that of the third parties on which Syndax depends, including delaying or otherwise disrupting Syndax's clinical trials and preclinical studies, manufacturing and supply chain, or impairing employee productivity; failure of our collaborators to support or advance collaborations or product candidates and unexpected litigation or other disputes. Moreover, Syndax operates in a very competitive and rapidly changing environment. Other factors that may cause our actual results to differ from current expectations are discussed in Syndax's filings with the U.S. Securities and Exchange Commission, including the "Risk Factors" sections contained therein. New risks emerge from time to time. It is not possible for Syndax's management to predict all risks, nor can Syndax assess the impact of all factors on its business or the extent to which any factor, or combination of factors, may cause actual results to differ materially from those contained in any forward-looking statement. In light of these risks, uncertainties and assumptions, the forward-looking events and circumstances discussed in this presentation may not occur and actual results could differ materially and adversely from those anticipated or implied. Except as required by law, neither Syndax nor any other person assumes responsibility for the accuracy and completeness of the forward- looking statements. Syndax undertakes no obligation to update publicly any forward-looking statements for any reason after the date of this presentation to conform these statements to actual results or to changes in Syndax's expectations.

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1Q catalyst updates set the stage for a transformative 2024

1Q milestones

Granted Priority Review for revumenib NDA submission under RTOR for R/R KMT2Ar acute leukemia

Granted Priority Review for axatilimab BLA submission in chronic GVHD after failure of at least two prior lines of systemic therapy

Completed enrollment of mNPM1 AML cohort in revumenib pivotal AUGMENT-101 trial

Looking ahead in 2024

PDUFA action date of September 26, 2024, for revumenib, followed by launch

PDUFA action data of August 28, 2024, for axatilimab, followed by launch

Pivotal revumenib AUGMENT-101 data in mNPM1 AML in 4Q

Additional revumenib combination data in frontline and R/R patients

Phase 3 frontline trial initiations for axatilimab and revumenib

Update from Phase 1 metastatic CRC trial in 2Q

KMT2Ar, KMT2A rearrangement; mNPM1, mutated nucleophosmin; RTOR, Real-time oncology

review; R/R, relapsed or refractory; AML, Acute myeloid leukemia; GVHD, Graft-versus-host3 disease; CRC, Colorectal cancer

Pivotal AUGMENT-101 trial: KMT2Ar AML/ALL filing under Priority Review; potential filing for mNPM1 in 1H25

Phase 1		Phase 2
Dose Escalation		Ongoing Pivotal Trials

			KMT2Ar
				AUGMENT-101-2A: KMT2Ar ALL
Adult and ped1				AUGMENT-101-2B:KMT2Ar AML
with R/R KMT2Ar	RP2D2
or mNPM1acute
leukemia			mNPM1
				AUGMENT-101-2C:mNPM1 AML

Primary endpoint

CR Rate (CR + CRh)

Expected Milestones

KMT2Ar
Enrollment completed
Topline data
Filing (RTOR)
mNPM1
Enrollment complete
Topline data	4Q24
Filing	1H25

Note: Patients taken to HSCT can restart treatment with revumenib post-transplant; Abbreviations: KMT2Ar, KMT2A rearrangement; mNPM1, mutated nucleophosmin
1	Allows patients ≥30 days of age	4
2	276mg q12h or 163mg q12h w/ strong CYP3A4 inhibitor
3	Completed enrollment of a sufficient number of KMT2Ar patients to support a registration filing

mNPM1 AML Phase 1 results suggest robust efficacy with durable, MRDneg responses

Phase 1

Dose Escalation

	n (%)
Total mNPM1 @ RP2D	14
CR/CRh	5 (36%)
MRDneg CR/CRh	5 (100%)
ORR	7 (50%)

No treatment related discontinuations

No grade 4 or 5 QTc events

Only differentiation syndrome ≤ grade 2 observed

3/7	1
(43%) of responders	patient restarted
proceeded to HSCT	revumenib post HSCT*

3/5	TRAEs
patients achieving	in-line with overall
CR/CRh maintained	AUGMENT-101 Phase
response beyond 6	1/2 experience
months, 2 for >22 months

Pivotal revumenib AUGMENT-101 data in

mNPM1 AML expected in 4Q24

• Data cutoff of July 24, 2023; 2023 amendment allowed patients to restart treatment with revumenib post-transplant following HSCT; mNPM1, Mutated nucleophosmin; HSCT, Haematopoietic stem cell transplant; RP2D, Doses that met

exposure equivalent of 226 mg q12h or 276mg q12h without strong CYP3A4 inhibitor or 113 mg q12h or 163 mg q12h with	5
strong CYP3A4 inhibitor

Revumenib could provide significant benefit in mNPM1 and KMT2Ar acute leukemias across the treatment paradigm

mNPM1 & KMT2Ar

acute leukemiaFrontlineMaintenance treatment paradigm

Revumenib clinical development program (KMT2Ar and mNPM1 acute leukemia) - ongoing trials

Pivotal

	BEAT AML		INTERCEPT
Phase 1/2	Rev + Ven/Aza		Rev Monotherapy Tx

Relapsed /

Refractory

AUGMENT-101

Rev Monotherapy

AUGMENT-102

Rev + Chemo

Rev + Intensive	Maintenance		SAVE
	Rev + Ven + INQOVI®
Chemo "7+3"

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Axatilimab may be a practice-changing intervention for cGVHD

Unique MOA for cGVHD

• First agent to target disease- causing macrophages to impact fibrosis & inflammation
• Potential synergy with SOC

High and durable ORR

• 74% ORR at 0.3 mg/kg
• 60% of patients treated at 0.3 mg/kg remained in response at 12mo

Well tolerated supporting broad use

• Low rate of SAEs and discontinuations at 0.3 mg/kg
• Antibody reduces potential for DDIs versus small molecule competitors

Enrolled population reflects real world

• Efficacy observed in patients following treatment with current SOC
• Option to switch to Q4W dose at 6mo

cGVHD, Chronic graft-versus-host disease; MOA, Mechanism of action; SOC, Standard of care; DDI, Drug-drug interactions; ORR, Overall response rate; Q4W, Every 4 weeks; SAEs, Serious adverse events

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Pre-launch priorities to maximize launch potential

1	Developing an efficient, effective and purpose-
built infrastructure and customer-facing model

2	Ensuring market access and patient support services are
	available at time of launch

3	Developing relationships with key stakeholders
including payors and healthcare providers

4	Delivering disease state awareness and education

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Revumenib's profile supports use as backbone therapy across treatment continuum - providing access to >$4B US market opportunity

Significant growth potential with indications in earlier lines of treatment

Market Opportunity ($ B)

Est. patient population

~ $1.5 - $2B market

R/R

KMT2Ar + mNPM1

Acute Leukemia

5,000 - 6,500

~ $1B market

1L "Unfit"

KMT2Ar + mNPM1 Acute Leukemia

~3,500

~ $2B market

1L "Fit"

KMT2Ar + mNPM1 Acute Leukemia

~5,500

> $4B market

Total

Source: Data on file; Redbook 2023

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Axatilimab has the potential to expand into additional high value indications and new geographies

2024 & Beyond

~215,000 US ~335,000 WW2

>35,000 WW1

~14,000 US1

Expansion into fibrotic indications: IPF POC* ongoing

Expansion into EU, Japan, ROW

R/R chronic GVHD: PDUFA action date set for August 28, 2024

Expansion into 1st L chronic GVHD: Jakafi® combo trial init 2024 Steroid combo trial init 2024

1 SmartImmunology Insights cGVHD report March 2020; 2 SmartImmunology Insights IPF report March 2020. * IPF trial will be conducted and funded by Syndax

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