The 19th Annual Needham Virtual Healthcare ConferenceApril 14, 2020

NASDAQ: MEIP

Forward-Looking Statements

• This presentation contains, and our officers and representatives may from time to time make, statements that are “forward-looking

statements” within the meaning of the safe harbor provisions of the U.S. Private Securities Litigation Reform Act of 1995. Examples of

forward-looking statements include, among others, statements regarding our development strategy; potential advantages of our product

candidates; the initiation and completion of preclinical and clinical studies and the reporting of the results thereof; the timing of regulatory

submissions and actions; the sufficiency of our existing cash; and all other statements relating to our plans, objectives, expectations and

beliefs regarding future performance, operations, financial condition and other future events (including assumptions underlying or

relating to any of the foregoing).

• These forward-looking statements rely on a number of assumptions concerning future events and are subject to a number of risks,

uncertainties, and other factors, many of which are outside of our control. Important factors that could cause our actual results and

financial condition to differ materially from those indicated in forward-looking statements include, among others: uncertainties relating to

the initiation and completion of preclinical and clinical studies; whether preclinical and clinical study results will validate and support the

safety and efficacy of our product candidates; the outcome of regulatory reviews of our product candidates; varying interpretation of

research and development and market data; the impact of the COVID-19 pandemic on our industry and individual companies, including

on our counterparties, the supply chain, the execution of our clinical development programs, our access to financing and the allocation of

government resources; risks and uncertainties relating to intellectual property and the other factors discussed under the caption “Item

1A. Risk Factors” in our most recent annual report on Form 10-K and our most recent quarterly report on Form 10-Q.

• Any forward-looking statement made by us in this presentation is based only on information currently available to us and speaks only as

of the date on which it is made. In addition, we operate in a highly competitive and rapidly changing environment, and new risks may

arise. Accordingly, you should not place any reliance on forward-looking statements as a prediction of actual results. We disclaim any

intention to, and undertake no obligation to, update or revise any forward-looking statement. You are urged to carefully review and

consider the various disclosures in our most recent annual report on Form 10-K, our most recent Form 10-Q and our other public filings

with the SEC since the filing of our most recent annual report.

2

Building a Leading Oncology Franchise

• 4 Clinical-Stage Oncology Programs: Focus On HemOnc

• 2 Candidates in Studies Intended to Support FDA Marketing

Approval Applications

• ME-401: TIDAL Study Supporting Accelerated Approval

Submission in r/r Follicular Lymphoma

• $104 Million to Advance Programs (as of Dec 31, 2020)

• $100M to be received from KKC Global Alliance

3

PROGRAMS INDICATION COMBINATIONCLINICAL PROOF

OF CONCEPT

MARKETING APPROVAL

STUDY

COMMERCIAL

RIGHTS

ME-401Oral P13K Delta

Inhibitor

Follicular Lymphoma

Relapsed/refractoryMonotherapy

U.S. co-promote; ex-

U.S. Kyowa Kirin

exclusive rights

B-Cell Malignancies

Relapsed/refractory

• Monotherapy

• Rituxan®(rituximab)

• Zanubrutinib2

VoruciclibOral CDK Inhibitor

B-Cell Malignancies

& AML

Relapsed/refractory

• Monotherapy

• Venclexta® (venetoclax)3

ME-344Mitochondrial Inhibitor

HER2-Breast Cancer

Treatment-naïve, early

stage

Avastin® (bevacizumab)4

Late-Stage Diversified Clinical Pipeline

1. Phase 2 study to support an accelerated approval marketing application with FDA. 2. Study arm initiated under clinical collaboration with BeiGene, Ltd. 3. Initiation of clinical studies is subject to opening of a new Investigational

New Drug Application with FDA 4. Investigator-initiated trial.

PracinostatHDAC Inhibitor

Acute Myeloid Leukemia

Treatment-naïveVidaza® (azacitidine)

Myelodysplastic Syndrome

Treatment-naïveVidaza® (azacitidine)

Phase 3 Pivotal Trial

Phase 2 Accelerated Approval Trial1

Clinical Collaboration

4

Pipeline of Compatibility Shift Towards Versatile Drugs in Potent Combinations

5

MEI Drug Candidates Select Combinations Potential Indications

FL

MCL

MZL

MDS

Solid Tumor

CLL/ SLL

AMLAzacitidine

Anti-angiogenic

BCL2i

BTKi

Anti-CD20ME-401

Voruciclib

ME-344

Pracinostat

DLBCL

B-cell Malignancies1

• >100K new CLL / NHL U.S. cases in 2018

• ~ 5% of cancers in the US

AML2

• ~20K new U.S. cases 2018

• 32% of adult leukemias

MDS2

• ≥ 10K U.S. cases annually

• 30% of MDS → to AML

MEI Retains Commercial Rights to Majority of Programs

Select Opportunities to Address Significant Unmet Needs

6

$1B + Markets

1. https://www.cancer.org/cancer/chronic-lymphocytic-leukemia/about/key-statistics.html; https://www.cancer.org/cancer/non-hodgkin-lymphoma/about/key-statistics.html; https://www.cancer.org/research/cancer-facts-statistics/all-cancer-facts-figures/cancer-facts-figures-2018.html# 2. https://www.cancer.org/cancer/acute-myeloid-leukemia/about/key-statistics.html; https://www.cancer.net/cancer-types/leukemia-acute-myeloid-aml/statistics; https://www.cancer.org/cancer/myelodysplastic-syndrome/about/key-statistics.html; https://www.mds-foundation.org/what-is-mds/

ME-401 ± Rituximab in Relapsed/Refractory

(R/R) B-cell Malignancies

7

$582Min potential development, regulatory and

commercial milestones

KKC exclusive ex-U.S. rights, MEI to received escalating tiered royalties starting in teens

U.S. COST SHARING, KKC responsible for incremental ex-U.S. costs

AGREED ON BROAD DEVELOPMENT PLAN for B-cell malignancies

Global License, Development and Commercialization Agreement Optimizes ME-401 Value

$100M upfront to MEI

8

50/50U.S. co-promote,

MEI books U.S. sales

The Time for PI3Kδ Has Come: Target Profile to Meet B-Cell Malignancy Medical Need

9

Low G3+ TEAEs

High Responses

Oral

Administration

Durable

Responses

ME-401

Low Discontinuation

Rate

10

ME-401 Fits the Profile of a New Treatment for B-Cell Malignancies

ME-401 data is from r/r follicular lymphoma patients in an ongoing Phase 1b study. Data cutoff: September 19, 2019

79% ORR

High Response Rates

>20 months

Durable Responses to Date(Median follow-up: 10.4 mo.)

<10%Low G3

TEAEs of Special Interest

4% Low Discontinuation Rate

for any TEAE

11

ME-401: Maintaining the Promise of PI3Kδ Inhibition1

In Development

1Data on File (ORR: n=39 on IS monotherapy. Safety: n=57 pts. on IS), 2ZYDELIG (idelalisib) [prescribing information]. Foster City, CA: Gilead Sciences, Inc (n=72 FL pts), 3ALIQOPA (copanlisib) [prescribing information]. Whippany, NJ: Bayer HealthCare Pharmaceuticals Inc (n=104 FL pts), 4COPIKTRA (duvelisib) [prescribing information]. Needham,

MA: Verastem, Inc (n=83 FL pts), 5Grade 3 neutrophil laboratory abnormalities.

Approved2, 3, 4

Note: These data are based on cross-trial comparisons and not based on any head-to-head preclinical studies or clinical trials. As a result, the values shown may not be directly comparable and do not report robust comparative analyses. ME-401 data is from ongoing Phase 1b study. Data cutoff is September 19, 2019

ME-401 (IS)

Overall Response

Rate (ORR)54% 59% 42% 79%

Diarrhea/Colitis 14% 5% 23% 7%

Rash 3% 2% 9% 2%

ALT/AST 19%/12% 2%/2% 8%/6% 2%/0%

Pneumonia/

Pneumonitis16% 14% 20% 2%

Neutropenia 25% 27% 42% 11%5

Discontinuation for

AE; any grade53% 16% 35% 4%

ME-401

12

ME-401

BCL2i2

BTKi1

ME-401 Emerging Profile: Potential for Broad Acceptance Across B-Cell Malignancies & Supports Combinations with Other Modalities

Note: These data are based on cross-trial comparisons and not based on any head-to-head preclinical studies or clinical trials. As a result, the values shown may not be directly comparable and do not report robust comparative analyses. ME-401 data is from an ongoing Phase 1b study evaluating patients on the intermittent schedule as a monotherapy or in combination with Rituxan® (rituximab). Data cutoff is Sept. 19, 2019

Discontinuation Rate: TEAEs (Any Grade)

10.0% (Range: 6.5% - 10.0%)

16.0% (Range: 9% - 16%)

14.6%R22

Diarrhea/

ColitisNeutropenia Anemia Thrombocytopenia

Pneumonia/

PneumonitisHemorrhage

Atrial

Fibrillation/Flutter

Secondary

Malignancy

Tumor Lysis

SyndromeFetal Toxicity

ME-401 7% 0% 0% 0% 2% 0% 0% 0% 0% -

BTKi 0.6%-5% 23%-27% 8%-10% 7%-8% 6%-13% 2%-4% 0.6%-4% 9%-12% 0% -

BCL2i 3%-4% 45%-62% 8%-18% 20-28% 8% 0% 0% 0% 2%-13% -R2 2.8% 50% 4.5% 2.3% 2.2% 0% 0% 0% ✔

1. Includes the FDA approved BTK inhibitors: IMBRUVICA (ibrutinib), CALQUENCE® (acalabrutinib) and BRUKINSA® (zanubrutinib). Rates of TEAE are from FDA labels and relate to safety databases for IMBRUVICA (n=1,124), CALQUENCE (n=1,029) and BRUKINSA (n=629), across clinical trials evaluating patients with CLL/SLL, MCL, WM, and MZL. 2. Rates of TEAEs are from the FDA label for VENCLEXTA (Venetoclax®) as indicated for the treatment CLL/SLL (n=758). 3. Rates of TEAEs are from the FDA label for Revlimid® (lenalidomide) as indicated for the treatment of follicular lymphoma and marginal zone (AUGMENT trial: n=176).

4.0%

High Volume of

Distribution

Tumor

Penetration

Tumor

Accumulation

Selective

Binding

Stable PI3Kδ

Binding

13

Supports Dose Schedule Optimization

ME-401: A Next-generation PI3Kδ Inhibitor with Potential to Redefine the Class

➢ Intermittent dosing (1 wk on / 3 wks off) begins at month 3

following 2 months of daily dosing

• ~80% disease responses occur by month 2

• PK/PD modeling projects ~2 weeks of tumor exposure above EC90

• Intermittent dosing expected to allow Treg repopulation

ME-401

ME-401 Copanlisib(Intravenous)

Idelalisib Duvelisib Parsaclisib Umbralisib

High VSS

VSS (L) ~7001

871 23.0 28.5 ~402

N/A

Cell Penetration

Cellular Association3

In Vivo Biologic

Activity IC50 (nM)4

61%

1

68%

NA

~10%

150

~10%

115

19%

NA

--

NA

1. Assumes average body weight of 70kg. 2. Incyte reported that “PK analysis has demonstrated that Parsaclisib distributes with body water. 3. Estimated from blood/plasma ratio. 4. Inhibition of basophil activation, except for Parsaclisib

which is inhibition of pAKT formation in SUDHL5 cells after incubation in blood from patients.

ME-401: Potential Superior Volume of Distribution and Cell Penetration Offer a Differentiation Explanation

14

Sources: ME-401: Moreno, et. al. Clinical Therapeutics (2018) and Moreno et. al., Targeted Oncology (2019). Copanlisib: CDER Multi-Discipline Review; Package insert. Idelalisib: CDER Clinical Pharmacology and Biopharmaceuticals Review; CHMP assessment report. Duvelisib: CDER Multi-Discipline Review; Package insert. Parsaclisib: Torres, et. al., Blood (2019). Umbralisib: Burris, et. al., Lancet Oncology (2018).

Note: These data are based on cross-trial comparisons and not based on any head-to-head preclinical studies or clinical trials. As a result, the values shown may not be directly comparable and do not report robust comparative

analyses.

ME-401

0

20

40

60

80

Plasma B-cell Tumor

4h

24h

0

25,000

50,000

75,000

100,000

Plasma B-cell Tumor

4h

24h

ME-401: Preferential Retention in Tumors

ng/ml ng/ml

ME-401 Idelalisib

15

Preferential Retention in Murine B-cell Tumors

Moreno et. al., Targeted Oncology (2019).

ME-401 and Idelalisib 50 mg/kg.

16

ME-401 at 60 mg

daily x2 cycles (28

Days)

N = 120

ME-401 at 60 mg for 1 wk

on / 3wks off

starting at Cycle 3 until

toxicity or PD If toxicity: Re-challenge

at resolution with IS

• Histologically confirmed diagnosis of FL, Grade 1, 2, or 3a

• FL, relapsed or refractory to 2 prior systemic therapies including an anti-CD20 antibody and chemotherapy

• No prior therapy with PI3Kδ inhibitors

• No histological transformation to an aggressive lymphoma

16

If PD: Change to CS

Phase 2 TIDAL Trial to Support Accelerated Approval Marketing Application – The Initial Opportunity in r/r FL

(NCT03768505)

ME-401

Select Combinatorial Potential of ME-401

17

Select Combinations Potential Indications

FL

MCL

MZL

CLL/ SLL

BCL2i

BTKi

Anti-CD20

ME-401

DLBCL

ME-401

Chronic Lymphocytic Leukemia

& Small Lymphocytic Lymphoma

Mantel Cell Lymphoma 4,500

DLBCL 22,000

Marginal Zone Lymphoma 6,000

Focus on Select B-Cell Malignancy Indications*

18

Follicular Lymphoma 15,000

(U.S. Only)

20,000

>65,000 Addressable

Patients Across Multiple

Indications

*U.S. incidence rates: Cancer.net, Cancer.org, Lymphoma.org (accessed on November 6, 2019).

$1B+Markets

ME-401

ME-401Conclusion

19

Many

Combinatorial

Options

Across B-Cell

Malignancies

Best-in-class

Potential

Emerging Profile

to Meet Need

Across B-cell

Disease and

Supports Broad

Acceptance

ME-401: Retaining the Promise of PI3Kδ

Voruciclib: Oral CDK Inhibitor with

Potent CDK9 Activity

20

Voruciclib

• Cyclin dependent kinases (CDKs)

are a family of enzymes involved in

cell cycle and transcription control

• CDK9 activates RNA Polymerase II

which is important for the

transcription of MCL-1 and c-Myc

• Voruciclib, an oral CDK inhibitor with

low nM inhibition of CDK9, 4/6 & 1,

causes potent suppression of both

MCL-1 and c-Myc

21

Voruciclib: a Novel, Oral CDK Inhibitor

Voruciclib

Voruciclib: Potential to Overcome Venetoclax Resistance

• Combination opportunities across multiple indications, including:

⎼ AML, CLL & DLBCL

221 Blood. 2016 Jun 23;127(25):3192-201 2 J Clin Oncol. 2017 Mar 10;35(8):826-833; 3 Sci Rep. 2017 21:7(1): 18007

Venetoclax inhibits BCL2

but can lead to

stabilization of MCL1

Voruciclib inhibits MCL1

via CDK9 inhibition

Increased MCL1 is an established venetoclax

resistance mechanism1

Voruciclib

THP-1 (24 h)

Contr

ol

VEN 1

000

nM

VEN 2

000

nM

VEN 4

000

nM

VOR 1

500

nM

VOR 2

000

nM

VOR 3

000

nM

VEN 1

000

+ VOR 2

000

VEN 2

000

+ VOR 2

000

VEN 1

000

+ VOR 3

000

VEN 2

000

+ VOR 3

000

0

50

100 AnnV+/PI+

AnnV+/PI-***

***

*** ***

CI<0.61A

nn

exin

V+

ce

lls (

%)

MOLM-13 (24 h)

Contr

ol

VEN 1

2.5

nM

VEN 2

5 nM

VEN 5

0 nM

VOR 5

00 n

M

VOR 1

000

nM

VOR 2

000

nM

VEN 1

2.5

+ VOR 1

000

VEN 2

5 +

VOR 1

000

VEN 1

2.5

+ VOR 2

000

VEN 2

5 +

VOR 2

000

0

20

40

60

80

100 AnnV+/PI+

AnnV+/PI-

CI<0.41

***

***

*** ***

An

ne

xin

V+

ce

lls (

%)

Voruciclib Synergizes with Venetoclax and Enhances Apoptosis in AML cell lines

V2

23Luedtke et al. Voruciclib, and Oral, Selective CDK9 Inhibitor, Enhances Cell Death Induced by the Bcl-2 Selective Inhibitor Venetoclax in Acute Myeloid Leukemia. ASH 2018

V2

Voruciclib

Voruciclib Synergizes with Venetoclax in a DLBLC Patient Derived Xenograft Model

24Dey J, Deckwerth TL, Kerwin WS, Casalini JR, Merrell AJ, Grenley MO, et al. Voruciclib, a clinical stage oral CDK9 inhibitor, represses MCL-1 and sensitizes high-risk diffuse large B-cell lymphoma to BCL2 inhibition. Sci Rep

2017;7:18007.

Days in Study

Ave

rag

e T

um

or

Vo

lum

e (

mm

3)

Vehicle

Voruciclib 200MPK

ABT-199 10MPK

ABT-199 10MPK + Voruciclib 200MPK

U2932

V2

Voruciclib

MEI Phase 1 Study: Daily Dosing Design in R/R B-Cell Malignancies and AML

• Study population⎼ Relapsed/Refractory B-cell Malignancies

⎼ AML After Treatment with Standard Therapy

• Dose escalation with standard 3+3 design

• Endpoints⎼ Safety and tolerability

⎼ Pharmacokinetics⎼ Biologic correlative studies

• BH3 profiling, MCL-1 expression (Dana Farber)

• Molecular mutations analysis (City of Hope)

⎼ Objective response rates⎼ CR/CRi rate

25

Voruciclib single agent

dose escalation

Venetoclax + Voruciclib dose

escalation

100

mg

150

mg

200

mg

50

mg

100

mg

150

mg

200

mgV2

Key Upcoming Milestones Across Portfolio

• ME-401

⎼ Data updates from Phase 1B combination studies in B-cell

malignancies (Mid 2020)

⎼ TIDAL, accelerated approval, study in R/R follicular lymphoma,

complete enrollment (H2 2020)*

• Voruciclib

⎼ Phase 1B study initiation in combination with Venetoclax

⎼ Phase 1 data updates (End 2020)

• ME-344

⎼ Evaluate development opportunities leveraging demonstration of

anti-tumor activity published at ASCO 2019

• Pracinostat

⎼ Phase 2 data from MDS dose-optimization study (Mid 2020)

26*Timing subject to developments related to the COVID-19 pandemic

The 19th Annual Needham Virtual Healthcare ConferenceApril 14, 2020

NASDAQ: MEIP