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

Post-ASCO 2021 Investor & Analyst

Event: Zandelisib in Focus NASDAQ: MEIP June 10, 2021 Exhibit 99.1

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.

MEI Pharma: Who We Are Clinical

Development Company Building a Leading Oncology Franchise with 4 Clinical-Stage Programs: Focus On HemOnc Zandelisib, Potential Best-in-Class PI3K Inhibitor in Phase 2 Study Intended to Support Accelerated Approval Applications with U.S. FDA

Well Capitalized with $164.6 Million* * As of March 31, 2021, MEI had $164.6 million in cash, cash equivalents, and short-term investments with no outstanding debt.

PROGRAMS INDICATION COMBINATION PHASE

1/1B PHASE 2 PHASE 3 COMMERCIAL RIGHTS Zandelisib Oral PI3K Delta Inhibitor Follicular & Marginal Zone Lymphomas Relapsed/refractory (2L+) Rituximab U.S. co-promote; ex-U.S. Kyowa Kirin exclusive rights Zandelisib Oral P13K Delta Inhibitor

Follicular & Marginal Zone Lymphomas Relapsed/refractory (3L+) Monotherapy U.S. co-promote; ex-U.S. Kyowa Kirin exclusive rights B-Cell Malignancies Relapsed/refractory Monotherapy Rituxan (rituximab) Brukinsa3 Voruciclib Oral CDK

Inhibitor B-Cell Malignancies & AML Relapsed/refractory Monotherapy Venclexta (venetoclax)4 ME-344 Mitochondrial Inhibitor Solid Tumors Avastin (bevacizumab)5 Pracinostat HDAC Inhibitor Myelodysplastic Syndrome Treatment-na ve

Vidaza (azacitidine) Late-Stage Diversified Clinical Pipeline TIDAL (FL) Study2 1. Study open for patient screening. 2. Phase 2 study intended to support accelerated approval marketing applications with FDA. 3. Study arm initiated under

clinical collaboration with BeiGene, Ltd. 4. Initiation of clinical studies is subject to opening of a new Investigational New Drug Application with FDA 5. Investigator-initiated trial. COASTAL Study1 TIDAL (MZL) Study2

Zandelisib Topline TIDAL Study Data on

Track to be Reported in the Fourth Quarter of CY2021 Enrollment Complete in Follicular Lymphoma Primary Efficacy Population The complete Phase 2 TIDAL study data are intended to be submitted to FDA to support accelerated approval applications

Zandelisib: Data Driven Advancement in

the Treatment of B-cell Malignancies

PI3K - Key Therapeutic

Target In B-cell Malignancies PI3K Is Involved in Multiple Critical Signaling Pathways Role of PI3K Inhibitors Active in B-cell NHL and CLL As single agent In combination Potential for combination regimens that enable time-limited

Options Tolerability Efficacy Comment:

Realizing PI3K Potential Lower potency Improved tolerability, but at the cost of lower efficacy Reduced activity on B and T cells Lower daily dose Attempts to improve tolerability without cost to efficacy Implies different

effects on B and T cells: not supported by current data Modify schedule Improved tolerability while maintaining efficacy With PI3Ki candidate that has properties allowing treatment breaks for TREG repopulation Why Prior Approaches with

Oral PI3K Inhibitors Came Up Short Continual dosing inhibits target in malignant B-cells . . . but continuous dosing leads to toxicity due to on-target TREG suppression

Zandelisib Unique Properties Fulfill

Potential of PI3K Inhibition DEBULKING Cycles 1&2 Daily for 56 days LONG-TERM DISEASE CONTROL Starting Cycle 3 7 days on / 21 days off Unique Dosing Schedule Zandelisib clinical data to date validate optimized dosing schedule potential

High response rates Durable responses Well tolerated regimen Potential for Best-in Class Clinical Profile Potency Active at nM concentrations Tight binding to the target Specificity Selective inhibition at clinically relevant dose PK

Characteristics Broad extravascular distribution Tumor accumulation Slower elimination from tumor vs plasma Moreno et al, Target Oncol 2019

Phase 1b multi-arm study with dose

finding and expansion cohorts Various B-cell malignancies Main eligibility criteria: ECOG 0 2, failure of 1 prior therapy, no prior PI3K or BTK therapy Disease assessment after 2, 4 and then every 6 cycles by Lugano and iwCLL criteria

~140 patients treated to date Phase 1b Study Evaluating Zandelisib as a Single Agent or in Combination with Rituximab or Zanubrutinib NCT02914938 Single agent in FL and CLL/SLL Combination with rituximab in iNHL, CLL/SLL, DLBCL Combination with

zanubrutinib in iNHL, MCL, DLBCL

Efficacy and Safety of the

PI3K Inhibitor Zandelisib (ME-401) on an Intermittent Schedule (IS) in Patients with Relapsed/Refractory Follicular Lymphoma (FL) with Progression of Disease within 24 Months of First-Line Chemoimmunotherapy (POD24) John M. Pagel1, Nishitha M.

Reddy2, Deepa Jagadeesh3, Anastasios Stathis4, Adam S. Asch5, Huda S. Salman6, Vaishalee P. Kenkre7, Jacob D. Soumerai8, Judith Llorin-Sangalang9, Igor Gorbatchevsky9, Joanne Li9, Andrew D. Zelenetz10 1Swedish Cancer Institute, Seattle, WA;

2Vanderbilt University Medical Center, Vanderbilt-Ingram Cancer Center, Nashville, TN; 3Cleveland Clinic, Taussig Cancer Institute, Cleveland, OH; 4Oncology Institute of Southern Switzerland, Bellinzona, Switzerland; 5University of Oklahoma Health

Sciences Center, Stephenson Cancer Center, Oklahoma City, OK; 6Stony Brook University School of Medicine, Stony Brook, NY; 7University of Wisconsin Carbone Cancer Center, Madison, WI; 8Massachusetts General Hospital Cancer Center, Boston, MA; 9MEI

Pharma, Inc., San Diego, CA; 10Memorial Sloan Kettering Cancer Center, New York, NY

Study Background 37 patients with FL

administered zandelisib on optimized schedule 18 with zandelisib alone 19 with zandelisib + rituximab Treatment regimen Zandelisib 60 mg daily x8 weeks then Days 1 7 of subsequent 28-day cycles Rituximab 375 mg/m2 weekly 4 then on Day 1

of Cycles 3 6 POD24 in 22/37 patients (59%) Progression of disease within 24 months of first line chemoimmunotherapy (POD24) associated with poor outcomes and shorter survival Data cut = Dec 2020

Demographics and Baseline

Characteristics POD24 N = 22 Non-POD24 N = 15 Total N = 37 Age, median (range) 61.5 (38 82) 63 (47 87) 62 (38-87) Prior therapies, median (range) 2 (1 4) 1 (1 5) 2 (1-5) Prior lines of therapy 1 2 7

(32%) 15 (68%) 9 (60%) 6 (40%) 16 (43%) 21 (57%) Refractory to prior rituximab 14 (64%) 1 (7%) 15 (41%) Tumor bulk 5 cm 11 (50%) 8 (53%) 19 (51%) POD24 Group More Heavily Treated and with More Refractory Disease

High Response Rate in All FL

Patients Including Both POD24 and Non-POD24 Groups POD24 N = 22 Non-POD24 N = 15 Total N = 37 Overall response rate (ORR) 18 (82%) 14 (93%) 32 (87%) Regimen Monotherapy Combination with rituximab 8/11 (73%) 10/11 (91%) 6/7 (86%) 8/8 (100%) 14/18

(78%) 18/19 (95%) Prior lines of therapy 1 line of prior therapy 2 lines of prior therapy 5/7 (71%) 13/15 (87%) 9/9 (100%) 5/6 (83%) 14/16 (88%) 18/21 (86%) CR rate, n (%) 4 (18%) 6 (40%) 10 (27%)

DOR POD24 Non-POD24 (n = 18) (n =

14) All (n = 32) Months since first response Prolonged Duration of Response in POD24

No Cumulative Toxicity Over Time

Grade 3 Adverse Events (AEs) in 2 Patients, n (%) N = 37 Neutropenia 6 (16) ALT/AST increased 3 (8) Rash 3 (8) Diarrhea 2 (5) Colitis 2 (5) Hypokalemia 2 (5) Hyponatremia 2 (5) COVID-19 infection* 2 (5) Discontinuation due to AEs in 3

patients (8%) Gr 3 skin rash Gr 3 diarrhea Gr 2 pneumonitis *One Grade 5 Covid-19 infection Low Incidence Grade 3 Adverse Events Treatment Well-tolerated: 8% Discontinuations Due to Adverse Events All FL on IS (n = 37) Time to Gr 3+ AESI

Median follow-up = 16.5 months

Z-R Mono (n = 18) (n = 14) Z-R Mono

(n = 19) (n = 18) Prolonged DOR and PFS with Zandelisib Rituximab Duration of Response Progression Free Survival

Maturing Data Support Registrational

Studies in iNHL - Phase 2 TIDAL and Phase 3 COASTAL Zandelisib Alone N = 18 Zandelisib-R N = 19 Overall response rate 78% (n=14) 95% (n=18) Median DOR NR NR Median PFS 15.7 mo NR Phase 2 TIDAL Phase 3 COASTAL NR="not

Zandelisib at 60 mg daily x2 cycles

(56 days) N = 120 Zandelisib at 60 mg 7 days on / 21 days off starting at Cycle 3 until toxicity or PD If toxicity: Re-challenge at resolution Histologically confirmed diagnosis of FL, Grade 1, 2, or 3a Relapsed or refractory to 2 prior systemic

therapies including an anti-CD20 antibody and chemotherapy No prior therapy with PI3K inhibitors No histological transformation to an aggressive lymphoma Also enrolling marginal zone lymphoma (N = 64) If PD: Change to daily Phase 2 TIDAL Trial

Intended to Support Accelerated Approval Marketing Application - The Initial Opportunity in Relapsed/Refractory Follicular Lymphoma NCT03768505

Phase 3 COASTAL Trial Intended to

Support Full Approval Globally - Confirmatory Study for US Accelerated Approval SCREENING EOT FOLLOW-UP PERIOD TARGET POPULATION Patients with R/R FL or MZL who received 1 line of prior systemic therapy Enrollment N=534 Randomized

1:1 ARM 1 Zandelisib + R for 6 cycles then zandelisib for 20 cycles ARM 2 R-B or R-CHOP for 6 Cycles EOT visit Efficacy follow-up Survival follow-up TREATMENT PERIOD NCT04745832

Moreno et al, Target Oncol 2019

Zandelisib Properties Enable Flexible Combination Usage DEBULKING + LONG-TERM DISEASE CONTROL 7 days on / 21 days off Starting Cycle 3 Unique Dosing Schedule Zandelisib clinical data to date validate optimized dosing schedule potential High response

rates Durable responses Well tolerated regimen Potential for Best-in Class Clinical Profile Potency Active at nM concentrations Tight binding to the target Specificity Selective inhibition at clinically relevant dose PK Characteristics Broad

extravascular distribution Tumor accumulation Slower elimination from tumor vs plasma

Initial Results of the Combination

of PI3K Inhibitor Zandelisib (ME-401) and the BTK Inhibitor Zanubrutinib in Patients with Relapsed or Refractory (R/R) B-cell Malignancies Jacob D. Soumerai1, Deepa Jagadeesh2, Huda S. Salman3, Izidore S. Lossos4, Nishitha M. Reddy5, Adam S.

Asch6, Vaishalee P. Kenkre7, John M. Pagel8, Daniel O. Persky9, Farrukh T. Awan10, Catherine S. Diefenbach11, Judith Llorin-Sangalang12, Igor Gorbatchevsky12, Wenying Huang12, Andrew D. Zelenetz13 1Massachusetts General Hospital Cancer Center,

Boston, MA; 2Cleveland Clinic, Taussig Cancer Institute, Cleveland, OH; 3Stony Brook University School of Medicine, Stony Brook, NY; 4University of Miami Health System, Sylvester Comprehensive Cancer Center, Miami, FL; 5Vanderbilt University Medical

Center, Vanderbilt-Ingram Cancer Center, Nashville, TN; 6University of Oklahoma Health Sciences Center, Stephenson Cancer Center, Oklahoma City, OK; 7University of Wisconsin Carbone Cancer Center, Madison, WI; 8Swedish Cancer Institute, Seattle, WA;

9University of Arizona, Tucson, AZ; 10UT Southwestern Medical Center, Dallas, TX; 11NYU Langone Health, Perlmutter Cancer Center, New York, NY; 12MEI Pharma, Inc., San Diego, CA; 13Memorial Sloan Kettering Cancer Center, New York, NY

Dual inhibition of PI3K and

BTK pathways displays synergistic activity* Full dose not needed to show synergy Combination therapy may overcome resistance to either agent *De Rooij, Blood 2015 Objective: Leverage zandelisib dose schedule in combination with zanubrutinib to

provide deeper and prolonged responses Result: Identification of optimized dosing regimen believed to capture synergy potential and optimize tolerability Potential of Dual Targeted Therapy with Zandelisib

Treatment in 28-day cycles

Zandelisib 60 mg daily x2 cycles then Days 1 7 in Cycles 3 Zanubrutinib 160 mg twice daily No DLT in the 28-day period In Cycle 2 1 MZL patient had Gr 3 AST/ALT with Gr 3 rash and discontinued due to recurrent rash 1 MCL patient had Gr

3 AST/ALT, recovered and referred to curative stem cell transplant Treatment in 28-day cycles Zandelisib 60 mg on Days 1 7 of all cycles Zanubrutinib 80 mg twice daily DLT period extended to 56 days In Cycle 2 2 patients had asymptomatic Gr 3

AST/ALT 1 FL successfully rechallenged 1 MZL discontinued for recurrent Gr 3 ALT Study Conduct Group A (N = 7) Group B (N = 13)

All N = 20 Group A N = 7

Group B N = 13 Age, median (range) 70 (44-85) 74 (44-85) 69 (55-83) Prior therapies, median (min-max) 2 (1-8) 2 (1-3) 2 (1-8) Diagnosis FL CLL/SLL MZL MCL DLBCL/HGBCL 8 (40%) 5 (25%) 2 (10%) 1 (5%) 4 (20%) 1

(14%) 3 (43%) 1 (14%) 1 (14%) 1 (14%) 7 (54%) 2 (15%) 1 (8%) 0 3 (23%) Tumor bulk 5 cm 6 (30%) 2 (29%) 4 (31%) Demographics and Baseline Characteristics

CR/CRi in 2/8 FL (25%) and 2/5 CLL

(40%) Longer follow-up needed to assess deepening response Evaluable n = 18 FL n = 8 CLL/SLL n = 5 MZL n = 2 MCL n = 1 DLBCL/HGBCL n = 2 ORR, n (%) 8 (100) 5 (100) 2 (100) 1 (100) 0 Group A 1 (100) 3 (100) 1 (100) 1 (100) 0 Group B 7 (100) 2 (100) 1

(100) 0 0 Disease Response in 100% of Patients with iNHL and CLL

Median follow-up 3.6 months for

Group A (range 0.6 21.3) 6.6 months for Group B (range 1.9 14.1) DIAGNOSIS DLBCL/HGBCL MZL CLL FL MCL 80 70 60 50 40 30 20 10 0 -10 -20 -30 -40 -50 60 -70 -80 -90 -100 SPD change from baseline (%) a = Group A a a a a a a Maximum Percent

Change in SPD from Baseline