Stemline Therapeutics, Inc.

Transcription

1 Stemline Therapeutics, Inc. NASDAQ: STML Corporate Presentation August 2018

2 2 Forward-Looking Statements This presentation includes statements that are, or may be deemed, forward-looking statements. In some cases, these forward-looking statements can be identified by the use of forward-looking terminology, including the terms believes, potentially, estimates, anticipates, expects, plans, intends, may, could, might, will, should, approximately or, in each case, their negative or other variations thereon or comparable terminology, although not all forward-looking statements contain these words. They appear in a number of places throughout this presentation and include statements regarding our intentions, beliefs, projections, outlook, analyses or current expectations. You should read carefully our Special Cautionary Notice Regarding Forward-Looking Statements and the factors described in the Risk Factors sections of our reports on Form 10-K and Form 10-Q filed with the Securities and Exchange Commission to better understand the risks and uncertainties inherent in our business.

3 Stemline Highlights Goal is to become a leading commercial stage biotechnology company ELZONRIS (Tagraxofusp; SL-401): Novel CD123-targeted therapy BLA filed, Priority Review granted, PDUFA date: 2/21/19 Possible approval in 1 st CD123+ indication (BPDCN) Clinical activity in 2 nd and 3 rd CD123+ indications (CMML, MF) Exploring additional indications, including possible CD123+ basket trial CD123 targeting: Multi-billion dollar market potential BPDCN Universe Hematologic Cancers Solid Cancers Autoimmune Abbreviations: BPDCN = blastic plasmacytoid dendritic cell neoplasm; CMML = chronic myelomonocytic leukemia; MF = myelofibrosis 3

4 4 Stemline Clinical Pipeline Program Target Indication IND Phase 1 Phase 2 BPDCN SL-401 single agent (Pivotal) PDUFA: 2/21/19 MPN (CMML and MF) SL-401 single agent Enrolling ELZONRIS IL-3R (CD123) AML (in CR, MRD+) Myeloma (r/r) SL-401 single agent SL pomalidomide + dex Enrolling Enrolling High risk MDS, Elderly AML SL azacitidine Enrolling (IST) SL-801 XPO1 Advanced solid tumors SL-801 single agent Enrolling SL-701 IL-13Ra2 EphA2 Survivin GBM (second-line) SL-701 single agent and + bevacizumab Completed BPDCN = blastic plasmacytoid dendritic cell neoplasm; MPN = myeloproliferative neoplasms; CMML = chronic myelomonocytic leukemia; MF = myelofibrosis; AML = acute myeloid leukemia; CR = complete response; MRD = minimal residual disease; r/r = relapsed/refractory; MDS = myelodysplastic syndrome; IST = investigatorsponsored trial; GBM = glioblastoma multiforme 1 To ensure continued patient access, Stemline is enrolling first-line and r/r BPDCN patients under the current protocol (Stage 4).

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6 % viable ELZONRIS is a Targeted Therapy Directed to CD123 ELZONRIS SL-401 Truncated diphtheria toxin payload IL-3 CD123 Elevated expression on BPDCN IL-3R/CD123 Cancer cell ELZONRIS Potent activity (femtomolar IC 50 ) against BPDCN ELZONRIS is a targeted therapy directed to IL-3Rα/CD123 CD123 overexpressed by BPDCN ELZONRIS is highly potent against BPDCN in vitro and in vivo Clinical activity in Phase 1/2 investigatorsponsored trial: 78% ORR; 5 CR and 2 PR in 9 evaluable BPDCN patients (Blood, 2014) CD123 Skin biopsy (IHC) SL-401 (fm) 6

7 ELZONRIS BPDCN

8 BPDCN Overview BPDCN Skin Lesions Background Nomenclature Highly aggressive hematologic malignancy Poor prognosis; median overall survival (OS) 8-14 months Named BPDCN by WHO in Derived from plasmacytoid dendritic cell (pdc) Previous names (prior to 2008) included: - Blastic NK cell leukemia/lymphoma - Agranular CD4+/56+ hematodermic neoplasm Diagnostic Signature Presentation Unmet Medical Need CD123 / CD4 / CD56 and other markers (TCL-1, CD303) Primary sites: bone marrow and skin Secondary sites: lymph nodes, viscera No approved therapies or standard of care Stem cell transplant (SCT) promising for select patients in remission BPDCN Bone Marrow H&E Riaz et al. Cancer Control, 2014; Pagano et al. Haematologica, 2013; Pemmaraju. Curr Hematol Malig Rep, 2017; Bueno et al., Haematologica 2004; Wang et al. Haematologica CD4 CD56 TCL1 CD123

9 Multiple Opportunities for Growth within BPDCN Universe BPDCN (EU) BPDCN Signature Similar patient size to US Filing Discussions Underway Maintenance Therapy (post-sct) (30%) x (16%) x new AML cases (EHA, 2016) Potential upside BPDCN (US) ~45% first-line BPDCN patients on ELZONRIS bridged to SCT Study Design In Process 9

10 ELZONRIS Pivotal Trial Results

11 11 BPDCN Trial Design Stage 1 (lead-in, dose escalation) Stage 2 (expansion) Stage 3 (pivotal, confirmatory) BPDCN (1L and R/R) 1 ELZONRIS (7, 9, 12, or 16 µg/kg) via IV infusion, days 1-5 of a 21-day cycle Key objectives: To determine optimal dose and regimen for Stage 2 BPDCN (1L and R/R) 2 ELZONRIS (12 µg/kg) via IV infusion, days 1-5 of a 21-day cycle Key objectives: To further define safety and efficacy BPDCN (1L) ELZONRIS (12 µg/kg) via IV infusion, days 1-5 of a 21-day cycle Key objectives: To confirm efficacy for registration To ensure ongoing access to ELZONRIS, BPDCN patients are being enrolled in an additional cohort, Stage 4 1 Stage 1 also enrolled AML (R/R) patients 2 In BPDCN, 12 µg/kg/day was highest tested dose (maximum tolerated dose not reached) and selected for Stage 2 Abbreviations: 1L = first-line; R/R = relapsed/refractory; IV = intravenous

12 12 Phase 2 Trial - All Stages (12 mg/kg/day) Line of Therapy 1L R/R 1L & R/R n ORR, n (%) 26 (90%) 9 (69%) 35 (83%) CR + CRc + CRi, n (%) 21 (72%) 5 (38%) 26 (62%) CR CRc CRi PR, n (%) 5 (17%) 4 (31%) 9 (21%) Bridged to SCT, n (%) 13 (45%) 1 (8%) 14 (33%) Allo Auto Primary endpoint met: Stage 3 CR + CRc rate of 54% (7/13) [95% CI: 25.1, 80.8] 1 In addition, in Stage 1 (lead-in, dose escalation), 3 BPDCN patients received ELZONRIS at 7mg/kg/day, of which there was 1 CR and 1 PR: ORR: 67% (2/3), CR + CRc + CRi rate = 33% (1/3). Abbreviations: ORR = overall response rate; CR = complete response; CRc (clinical CR) = absence of gross disease in non-skin organs with marked clearance of skin lesions with residual abnormality; CRi = CR with incomplete hematologic recovery; CI = confidence interval; PR = partial response; SCT = stem cell transplant; Allo = allogeneic; Auto = autologous; mswat = modified Severity-Weighted Assessment Tool; RFS = relapse free survival.

13 Safety and Tolerability All ELZONRIS Clinical Trials (12 mg/kg/day) (n=148) Most Common Adverse Events (AEs)(>15% Treatment-Related AEs, TRAEs) All Grades n (%) TRAEs n (%) Preferred Term TRAEs All AEs Gr 1-2 Gr 3 Gr 4 Gr 5 ALT increased 65 (43.9%) 80 (54.1%) 31 (20.9%) 34 (23.0%) 0 (0.0%) 0 (0.0%) AST increased 65 (43.9%) 74 (50.0%) 30 (20.3%) 31 (20.9%) 4 (2.7%) 0 (0.0%) Hypoalbuminaemia 65 (43.9%) 73 (49.3%) 64 (43.2%) 1 (0.7%) 0 (0.0%) 0 (0.0%) Thrombocytopenia 39 (26.4%) 48 (32.4%) 7 (4.7%) 8 (5.4%) 24 (16.2%) 0 (0.0%) Nausea 38 (25.7%) 70 (47.3%) 37 (25.0%) 1 (0.7%) 0 (0.0%) 0 (0.0%) Pyrexia 33 (22.3%) 60 (40.5%) 33 (22.3%) 0 (0.0%) 0 (0.0%) 0 (0.0%) Fatigue 30 (20.3%) 67 (45.3%) 26 (17.6%) 4 (2.7%) 0 (0.0%) 0 (0.0%) Weight increased 28 (18.9%) 42 (28.4%) 28 (18.9%) 0 (0.0%) 0 (0.0%) 0 (0.0%) Chills 26 (17.6%) 40 (27.0%) 25 (16.9%) 1 (0.7%) 0 (0.0%) 0 (0.0%) Capillary leak syndrome (CLS) 1 25 (16.9%) 25 (16.9%) 16 (10.8%) 5 (3.4%) 3 (2.0%) 1 (0.7%) Hypotension 23 (15.5%) 36 (24.3%) 17 (11.5%) 5 (3.4%) 1 (0.7%) 0 (0.0%) Oedema peripheral 22 (14.9%) 57 (38.5%) 21 (14.2%) 1 (0.7%) 0 (0.0%) 0 (0.0%) 1 0.7% (1/148) for all trials (12mg/kg/day) and 1.6% (3/182) for all trials (all doses) were grade 5. A myocardial infarction, grade 5, was also reported in a patient who experienced a grade 4 CLS 13

14 Individual patients Best Response and Treatment Duration Stages 1 and 2: First-line BPDCN (12 mg/kg/day) Stage 3: First-line BPDCN (12 mg/kg/day) CR CR CRc CR PR CR CR CR CRc CR CRi CRc PR CRi CR CR Allo Auto Auto Allo Allo Allo Auto ELZONRIS Stem cell transplant (SCT) Receiving ELZONRIS, ongoing CRc CR CR CR CRc CRc CRc PR PR SD SD PR Allo Allo Allo Allo Allo Allo ELZONRIS Stem cell transplant (SCT) Off study in remission Time (Months) As of September 25, Time (Months) 1 Patient relapsed off study at 7.3 months.

15 Overall Survival (OS) EHA 18 First-line BPDCN (12 mg/kg/day) - Stages 1, 2, and 3 (n=29) Median OS: Not reached Long-term survivors (median follow up: 13.8 months ( months) 15

16 ELZONRIS: Prelaunch Activities

17 Critical Elements of ELZONRIS Launch Prepare the Product Prepare the Market Prepare the Organization Collect comprehensive. Stakeholder insights to inform product strategy Generate meaningful evidence that translates to clinical practice Prepare for and secure regulatory approval Establish effective value proposition and messages that resonate Maximize commercial lifecycle potential Understand market to define success factors & implications for launch Build advocacy w ith stakeholders to drive adoption & to limit barriers Energize effective customeroriented commercial team Achieve organizational alignment on success requirements and strategy Implement optimal supply chain Create infrastructure and processes to enable seamless execution HTA Planning Clinical Trial Strategy Registration Package Target Product Profile Geographic Sequencing Market Definition & Landscaping Unbranded Campaign & Communication Commercial Model Design Franchise Integration Manufacturing Strategy Launch Gov ernance Physician Awareness, Trial, Usage Winning Label Design Trade Name Registration Positioning Lifecycle Planning Competitiv e Intelligence KOL Identification & Planning Customer-Facing Team Design Rev enue Forecasting Demand Planning & Forecasting ERP Platform Update & Integration Patient Affordability & Unmet Needs Registration Trial Design Adv isory Committee Meetings Targeted Messaging Formulation Strategy Key Stakeholder Mapping Congress/ Symposia Planning & Exec. Incentiv e Compensation Planning Integrated Launch Planning Trade & Distribution Strategy CRM System Payer Market Access Requirements Phase 3b Trial Design Label Negotiation Pricing Strategy Dev ice Strategy Public Policy Analysis Publication Planning & Exec. Field Team Hiring & On-boarding Launch Risk Mitigation Planning Packaging Performance Reporting System Pharmacist Perspectiv es Post-Marketing Surv eillance Risk Management Payer Value Proposition Patient Adherence Strategy Patient Journey Patient Adv ocacy Plan. & Engagement Key Account Segmentation Launch Budgeting Contracting & Tendering Strategy Team-Up Design Caregiv er Analysis Comparativ e Effectiv eness Research Pharmacov igilance Branding Partner Identification & Licensing Strategic Segmentation MSL Engagement Planning Targeting & Call Planning Key Performance Indicators Patient Support Hub Site-of-Care Analysis Inv estigator Initiated Studies Branded Campaign & Communication Market Access Landscaping Medical Education Field Team Training Promotion Mix Optimization Market-Lev el CSFs Inv estor Relations Public Relations Sampling Patient Access Programs

18 BPDCN Awareness CD123 Testing 18

19 BPDCN Awareness Impressions By Audience ~1.7 million impressions to be delivered in

20 ELZONRIS Market Expansion Opportunities (Beyond BPDCN)

21 ELZONRIS: MPN: CMML and MF

22 MPN Trial Design Stage 1 Lead-in (Completed) MPN: CMML, MF, SM, and PED ELZONRIS (7, 9, or 12 mg/kg) via IV infusion, days 1-3 of a 21-day cycle (cycles 1-4), a 28-day cycle (cycles 5-7); a 42-day cycle thereafter Key objectives: To determine optimal dose and regimen for Stage 2 Stage 2 Expansion ( Enrolling) MPN: CMML or MF without evidence of transformation ELZONRIS (12 mg/kg) 1 via IV infusion, days 1-3 of a 21-day cycle (cycles 1-4), a 28-day cycle (cycles 5-7); a 42-day cycle thereafter Key objectives: To further define safety and efficacy Select inclusion criteria Patient population Stage 1 - Advanced, high-risk MPN, including CMML, MF, SM, and PED Stage 2 - CMML or MF without evidence of transformation Age 18; ECOG PS 0-2 Adequate baseline organ function, including: LVEF LLN, creatinine 1.5 mg/dl, albumin 3.2 g/dl, bilirubin 1.5 mg/dl, AST/ALT 2.5 times ULN, creatine phosphokinase (CPK) 2.5 times ULN, ANC /L 1 12 mg/kg/day was highest tested dose (MTD not reached) and selected for Stage 2 Abbreviations: CMML = chronic myelomonocytic leukemia; MF = myelofibrosis, SM = systemic mastocytosis; PED = primary eosinophilic disorders; IV = intravenous; MTD = maximum tolerated dose; ECOG = Eastern Cooperative Oncology Group; LVEF = left ventricular ejection fraction; AST/ALT = aspartate/alanine aminotransferase; ULN = upper limit of normal; ANC = absolute neutrophil count 22

23 Safety Profile - CMML and MF CMML MF Preferred Term Most Common Adverse Events ( 15% of treatment related adverse effects, TRAEs) All Grades n (%) TRAEs n (%) TRAEs All AEs G1 & 2 G3 G4 G5 Hypoalbuminemia 6 (37.5) 8 (50.0) 6 (37.5) Nausea 6 (37.5) 7 (43.8) 5 (31.3) 1 (6.3) Vomiting 5 (31.3) 8 (50.0) 5 (31.3) Fatigue 4 (25.0) 7 (43.8) 4 (25.0) Oedema peripheral 4 (25.0) 9 (56.3) 4 (25.0) Thrombocytopenia 4 (25.0) 4 (25.0) -- 2 (12.5) 2 (12.5) Back pain 3 (18.8) 7 (43.8) 3 (18.8) Capillary leak syndrome 3 (18.8) 3 (18.8) 3 (18.8) Weight increased 3 (18.8) 5 (31.3) 3 (18.8) Most Common Adverse Events ( 15% of treatment related adverse effects, TRAEs) Preferred Term All Grades n (%) TRAEs n (%) TRAEs All AEs G1 & 2 G3 G4 G5 Hypoalbuminemia 4 (26.7) 5 (33.3) 4 (26.7) Thrombocytopenia 4 (26.7) 5 (33.3) 2 (13.3) 1 (6.7) ALT increased 3 (20.0) 4 (26.7) 3 (20.0) Anemia 3 (20.0) 6 (40.0) -- 3 (20.0) Dizziness 3 (20.0) 6 (40.0) 3 (20.0) Fatigue 3 (20.0) 7 (46.7) 2 (13.3) 1 (6.7) Headache 3 (20.0) 4 (26.7) 3 (20.0) Nausea 3 (20.0) 7 (46.7) 3 (20.0)

24 CMML EHA 18 Pt # Dose (μg/kg/d) CMML type Line Prior Tx Bone Marrow Spleen 1 Best Baseline Best response Baseline (BM BMCR response (BM blast (cm) blast %) (cm) %) CMML-1 3 HMA CMML-1 2 HMA 6 0 6% 0% CMML-2 2 PST % 1% CMML-1 2 HMA CMML-2 2 HMA 18 N/A CMML-2 2 PST CMML-2 2 HMA CMML-1 2 PST 8 N/A CMML-1 2 HMA CMML-1 2 HMA CMML-1 2 PST CMML-2 2 PST CMML-2 2 PST CMML-1 3 HMA; Clofarabine 0 3 N/E CMML-1 1 PST 6 Pending N/E CMML-1 2 HMA; SCT Pending Pending N/E No splenomegaly No splenomegaly No splenomegaly No splenomegaly No splenomegaly No splenomegaly Spleen responders 100% (10cm 0cm) 100% (5cm 0cm) 100% (4cm 0cm) 100% (2cm 0cm) 100% (2cm 0cm) 50% (20cm 10cm) 36% (22cm 14cm) 21% (14cm 11cm) N/E N/E N/E N/E N/E N/E No splenomegaly Pending N/E No splenomegaly Pending N/E 100% (8/8) spleen responses in evaluable patients - 75% (6/8) had reduction of 50% - 60% (3/5) with baseline 5cm had reduction 50% - 2 bone marrow complete responses (BMCRs) Spleen response All Evaluable 1 5cm BCM 1 Patients with palpable spleen at baseline 2 Patients without palpable spleen at baseline BCM = below costal margin (by physical exam); N/E = not evaluable Not evaluable 2 n All reductions Reductions 50% 8 (100%) 5 (100%) N/E 6 (75%) 3 (60%) N/E HMA = hypomethylating agent; PST = prior systemic therapy 1 Measured by physical exam (cm below costal margin [BCM]) 24

25 25 Next Steps - CMML ELZONRIS monotherapy demonstrated efficacy (bone marrow complete responses and improvements in splenomegaly) with a manageable safety profile in patients with relapsed/refractory CMML, an area of high unmet medical need - Patient enrollment and follow up continues 100% (8/8) of evaluable patients had reduction in baseline splenomegaly - 75% had reduction by 50% - 60% with baseline spleen size 5cm had reduction by 50% - 2 bone marrow CRs Most common TRAEs include hypoalbuminemia (38%), thrombocytopenia (25%), and fatigue (25%). Most common TRAEs, grade 3+, include thrombocytopenia (25%) and nausea (6%) CD123 is expressed by chronic myelomonocytic leukemia (CMML). Notably, CD123+ plasmacytoid dendritic cells (pdcs) have been reported in the bone marrow microenvironment of certain malignancies where they may play a pathogenic role Given this potential dual role of CD123, ELZONRIS may offer a novel therapeutic approach in CMML Based on these encouraging results, registrational trial designs in patients with relapsed/refractory CMML are being formulated

26 Myelofibrosis (MF) EHA 18 Pt Platelets Dose (μg/kg/d) Line Prior Tx (baseline, 10^9/L) Baseline (cm) Spleen 1 Best Response (cm) JAKi JAKi JAKi PST; investig. agent JAKi; lenalidomide JAKi JAKi; 2 invest. agents JAKi; prep for SCT JAKi JAKi PST PST JAKi Spleen Responders 100% (5cm 0cm) 47% (19cm 10cm) 46% (35cm 19cm) 33% (30cm 20cm) 29% (17cm 12cm) 29% (14cm 10cm) JAKi; HMA, hydrea 35 No splenomegaly N/E PST 56 No splenomegaly N/E JAKi = JAK inhibitor; HMA = hypomethylating agent; SCT = stem cell transplant; PST = prior systemic therapy; N/E = not evaluable 1 Measured by palpation (cm below costal margin) 50% (6/12) spleen responses All 6 had reductions of at least 29% in spleen size 33% (4/12) with baseline 5cm had reduction of 33% in spleen size 25% (3/12) with baseline 5cm had reduction of 35% in spleen size Spleen response Evaluable 1 Not evaluable 2 5cm BCM n 12 3 Reductions 29% 6 (50%) N/E Reductions 33% 4 (33%) N/E Reductions 35% 3 (25%) N/E 1 Patients with baseline splenomegaly ( 5cm BCM) 2 Patients without baseline splenomegaly (<5cm BCM) BCM = below costal margin (by physical exam); N/E = not evaluable 26

27 27 Next Steps MF ELZONRIS monotherapy demonstrated efficacy (improvements in splenomegaly), with a manageable safety profile, in patients with relapsed/refractory MF, an area of high unmet medical need - Patient enrollment and follow up continues 50% of evaluable patients, with baseline spleen size 5cm, had reduction in baseline splenomegaly - 33% had reduction by 33% - 25% had reduction by 35% Most common TRAEs include hypoalbuminemia and thrombocytopenia (each 27%), and alanine aminotransferase increased, anemia, dizziness, fatigue, headache and nausea (each 20%). Most common TRAEs, grade 3+, include anemia (20%) and thrombocytopenia and fatigue (each 7%) CD123 is expressed by MF. Notably, CD123+ plasmacytoid dendritic cells (pdcs) have been reported in the bone marrow microenvironment of certain malignancies where they may play a pathogenic role Given the dual role of CD123, ELZONRIS may offer a novel therapeutic approach in MF Based on these encouraging results, next steps for the program are being evaluated including single agent, combination, and registration-directed trials in patients with relapsed/refractory MF

28 28 Milestones ELZONRIS Program Milestone Estimated Timeframe ELZONRIS BPDCN ELZONRIS Additional indications Pre-BLA meeting Agreement with FDA on rolling BLA submission Hire commercial leadership team including Head of Sales and Head of Reimbursement & Access Disease awareness campaign and market shaping operational plan launched Complete submission of rolling BLA Acceptance of BLA by FDA EMA pre-maa meeting 2H18 PDUFA Date February 21, 2019 Potential MAA filing (EU) Data presentations at scientific meetings Formulate registrational strategy (CMML and/or MF) Initiate pivotal trial in additional indication(s) 1H19 Mid-18 and 2H18 4Q18-1Q19 2H19

29 SL-801

30 30 SL-801: Overview SL-801 Novel, oral, small molecule inhibitor of XPO1 (Exportin 1) XPO-1 Target Key nuclear transport oncogene Over-expressed by variety of solid and liquid cancers Clinically-validated target in multiple cancer types SL-801: Novel and Differentiated Novel molecular structure Reversibly inhibits XPO1 Potential for safety and therapeutic window benefit Phase 1 Trial Patients with advanced solid tumors Data presented at ASCO 2018 Dose escalation; enrollment ongoing

31 31 SL-801: Rationale XPO1 inhibition may be a promising therapeutic strategy in certain KRAS-mutant cancers

32 32 SL-801: Study Design Stage 1 (Dose-escalation) - Enrollment Ongoing Advanced solid tumors SL-801 orally administered - Dose escalation (mg/day) o 5, 10, 20, 30, and by 5 mg increments thereafter - D1-4 and D8-11 of a 21-day cycle - Standard 3x3 design Endpoints - Safety and tolerability - DLT and MTD - ORR, DCR, DoR, PFS and OS Six sites in the US Stage 2 (Expansion) - Not started yet Disease-specific cohorts (up to 4 cohorts) - ~20 patients per cohort SL-801 orally administered - Dose and regimen to be selected from Stage 1 Endpoints - ORR - Safety profile - CR, DoR, PFS, OS Signal detection for subsequent registration-directed Phase 2 trials DLT = dose-limiting toxicity; ORR = overall response rate; DCR = disease control rate; DoR = duration of response; PFS = progression-free survival; OS = overall survival; MTD = maximum tolerated dose; CR = complete response

33 Age, years Median [range] 64 [39-76] Gender [n, (%)] Female 18 (51) Lines of therapy prior to the study [n, (%)]* 1 st Line 3 (9) 2 nd Line 7 (21) 3 rd Line 6 (18) 4 th Line 18 (53) RAS mutation [n, (%)] KRAS mutation: Yes 5 (14) No 9 (26) Unknown 19 (54) Other mutation: 2 (6) ECOG performance status [n, (%)] 0 10 (28) 1 23 (66) 2 2 (6) Follow-up time on study, months Median [range] 1.4 [ ] Demographics - ASCO 18 Heavily pre-treated patients: 71% patients were 3 rd line or greater Wide spectrum of solid tumors, including GI, breast, lung, neuroendocrine, ovarian, et al * One patient did not have their systemic therapy history available 33 Cancer Diagnosis Colorectal cancer (CRC) 5 Breast cancer 4 Non-small cell lung cancer (NSCLC) 3 GI adenocarcinoma (GI Adeno) 3 Neuroendocrine (Neuro-endo) 3 Pancreatic cancer 2 Adenoid Cystic Carcinoma (ACC) 2 Ovarian carcinoma 2 Squamous cell carcinoma (SCC) 2 Biliary 1 Renal 1 Bladder 1 Basal cell carcinoma (BCC) 1 Small bowel 1 Mesothelioma (Mesoth) 1 Leiomyosarcoma (LMS) 1 Appendix carcinoma 1 Paraganglioma 1 n

34 34 Safety and Tolerability - ASCO 18 Treatment Related Adverse Events (AEs) (n=35) Most Common Treatment Related Adverse Events (TRAEs, 15%) All Grades n (%) TRAEs n (%) Preferred Term TRAEs All AEs G1 & 2 G3 G4 G5 Nausea 19 (54.3) 20 (57.1) 16 (45.7) 3 (8.6) No DLT s reported No MTD Dose escalation ongoing Enrolling 10 th cohort (60 mg/day) Vomiting 13 (37.1) 20 (57.1) 12 (34.3) 1 (2.9) Fatigue 10 (28.6) 14 (40.0) 10 (28.6) Diarrhea 8 (22.9) 12 (34.3) 6 (17.1) 2 (5.7) Decreased appetite 7 (20.0) 10 (28.6) 7 (20.0) As of 30-Apr-18. Investigator-assessed data; unaudited Additionally, there was a one grade 3 TRAE of acute kidney injury reported at 30 mg/day dose level and one grade 3 TRAE of ne utropenia reported at 10 mg/day dose level

35 35 Best Response - ASCO 18 Dose Tumor Histology Best Response No. of lesions Sum of target lesions (measurable) Screening (mm) Best Response (mm) % Δ of target lesions Time to Best Response Last dose received 30 mg Neuro-endo SD % C2 C6 30 mg GI adenocarcinoma SD % C4 C7 40 mg BCC SD % C2 C14 40 mg Breast SD % C6 C6 35 mg NSCLC % C2 C2 55 mg Paraganglioma % C2 C3 5 mg CRC 1 SD % C2 C6 35 mg Biliary SD n/a n/a - C4 10 mg SCC SD C2 C4 40 mg Mesothelioma SD % C2 C2 45 mg GI Adeno SD % C2 C4 As of 30-Apr Investigator-assessed data; unaudited SD = stable disease; (-) = reduction; (+) = increase 1 Patient with KRAS mutation present at screening

36 Best Response and Treatment Duration - ASCO 18 Cancer Type BCC Neuroendo GI Adeno Breast CRC Neuroendo Small Bowel Biliary Paraganglioma GI Adeno SCC CRC GI Adeno Breast SCC NSCLC Mesothelioma NSCLC Breast CRC Ovarian LMS Pancreas CRC ACC - Parotid NSCLC Ovarian Neuroendo ACC Head & Neck Breast Bladder Pancreas CRC Appendix Renal Line of Therapy * SD SD SD SD SD SD SD SD SD e a a a d a b d d d b a a a a a d a a a a a a a c b a a d a a a a a b c d e Ongoing, receiving SL-801 In addition (not shown): 3 recently enrolled patients (10 th cohort: 60 mg) are receiving SL-801, ongoing 55 mg cohort 50 mg cohort 45 mg cohort 40 mg cohort 35 mg cohort 30 mg cohort 20 mg cohort 10 mg cohort 5 mg cohort a Discontinued, disease progression Discontinued, PI decision Discontinued, patient death, unrelated to SL-801 Discontinued, consent withdrawn Discontinued, AE As of April 30, Investigator-assessed data; unaudited. Time from C1D1 to end of treatment or ongoing * One patient did not have their systemic therapy history available Months

37 37 SL-801: Trial Status and Next Steps Next Steps Dose escalation continues - 10 th cohort (60 mg/day) enrolling Further updates expected later this year ASCO 2018 #2560 Interim Results from a Phase 1 Trial of SL-801, a Novel XPO-1 Inhibitor, in Patients with Advanced Solid Tumors J. Wang 1, J. Nemunaitis 2, E.G. Chiorean 3, P. Lorusso 4, K. Courtney 5, D. Qi 6, A. Olguin 6, J. Bullington 6, M. Sardone 6, V. Dunn 6, S. Shemesh 6, J. Chen 6, C. Brooks 6, T.M. Bauer 7 1 Florida Cancer Specialists, Sarasota, FL; 2 Mary Crowley Cancer Research Center, Dallas, TX; 3 University of Washington, Fred Hutchinson Cancer Research Center, Seattle, WA; 4 Yale Cancer Center, New Haven, CT; 5 University of Texas Southwestern Medical Center, Dallas, TX; 6 Stemline Therapeutics, New York, NY; 7 Tennessee Oncology, Nashville, TN Introduction and Highlights Phase 1 trial of SL-801, a novel XPO1 inhibitor, in heavily pre-treated patients with solid tumors Manageable safety and tolerability profile, largely grade 1-2 adverse events (AEs), to date No dose limiting toxicity (DLT) or maximum tolerated dose (MTD) reached Dose escalation ongoing; 10 th cohort (60 mg/day) currently enrolling Multiple cases of stable disease (SD) in a heavily pretreated solid tumor patient population Pharmacokinetic (PK) analyses suggest dose-dependent increases in exposure; studies ongoing Ideal therapeutic dose not yet determined as dose escalation continues Further updates expected this year Given favorable data profile thus far with SL-801, coupled with clinical validation of the XPO1 target, additional SL-801 trials, including in hematologic cancers and combination studies, planned SL-801 Background Background SL-801 is an orally administered, novel small molecule XPO1 (Exportin 1) inhibitor XPO1 is a key nuclear transport oncogene overexpressed in a variety of cancers Inhibition of XPO1 has been clinically validated in multiple cancer types SL-801 demonstrated potent in vitro and in vivo activity against a wide array of solid and hematologic cancer models SL-801 reversibly inhibits XPO1 offering the potential for a favorable therapeutic window A Phase 1 trial of SL-801 monotherapy in patients with advanced solid tumors is underway (NCT# ) Results from the ongoing dose escalation trial are reported here Select inclusion criteria Inclusion / Exclusion Criteria Advanced (metastatic or locally advanced and unresectable) relapsed or refractory solid tumors with histologic evidence Measurable disease and evaluable by RECIST 1.1 ECOG PS of 0-2 Adequate organ function, including: - Creatinine 1.5x ULN, albumin 2.5 g/dl, bilirubin 1.5x ULN, AST/ALT 2.5x ULN ( 5x for hepatic metastases), prothrombin time 1.5x ULN (and partial thromboplastin time 1.5xULN) Adequate hematologic function, including: - ANC 1.5x10 9 /L, Hgb 8 g/dl (w/o RBC transfusions within prior 14 days), platelet count 100x10 9 /L (w/o platelet transfusions within prior 14 days) Select exclusion criteria Persistent clinically significant ( G2) toxicities from prior anticancer therapies (excluding G2 chemotherapy-related neuropathy, and G2-3 lab abnormalities if not associated with symptoms and not considered clinically significant by PI) Chemotherapy, external-beam radiation or other systemic anticancer therapy within prior 28 days to first dose Prior treatment with SL-801 or another drug that inhibits XPO1/CRM1 pathway Active secondary malignancy that may confound assessment of study endpoints Clinically significant cardiovascular disease, uncontrolled clinically significant pulmonary disease, suspected brain or leptomeningeal metastases Immunosuppressive therapy for a prior organ transplant Uncontrolled intercurrent illness Infection with HIV or chronic Hep B or Hep C Demographics Heavily pre-treated patients: 71% patients were 3 rd line or greater Wide spectrum of solid tumors, including GI, breast, lung, neuroendocrine, ovarian, et al Dose Tumor Histology Best Response Best Response No. of lesions Sum of target lesions (measurable) Screening (mm) Best Response (mm) % Δ of target lesions Time to Best Response Last dose received 30 mg Neuro-endo SD % C2 C6 30 mg GI adenocarcinoma SD % C4 C7 40 mg BCC SD % C2 C14 40 mg Breast SD % C6 C6 35 mg NSCLC % C2 C2 55 mg Paraganglioma % C2 C3 5 mg CRC1 SD % C2 C6 35 mg Biliary SD n/a n/a - C4 10 mg SCC SD C2 C4 40 mg Mesothelioma SD % C2 C2 45 mg GI adenocarcinoma SD % C2 C4 As of 30-Apr Investigator-assessed data; unaudited SD = stable disease; (-) = reduction; (+) = increase 1 Patient with KRAS mutation present at screening Pharmacokinetics Pharmacokinetic (PK) analyses suggest dose-dependent increases in SL-801 exposure XPO1 Background XPO1 is the key mediator of nuclear-cytoplasmic transport and is involved with the export of more than 200 nuclear proteins, including: tumor suppressor proteins (p53, APC, Rb, BRCA1, FOXO family proteins) cell cycle inhibitors (p21/cip1, p27/kip1) transcription factors (ATF2) oncogenic proteins (CIP2A, Erk) immune response regulators (IkBa) molecular chaperone proteins (hsp90) 1,2 XPO1 also exports specific subsets of messenger ribonucleic acid (mrna) via export adaptor proteins 3 Mislocalization of a nuclear protein into the cytoplasm can render it ineffective as a tumor suppressor 4 XPO1 is overexpressed in various solid tumors, including breast, cervical, ovarian, and pancreatic cancers, glioma, and osteosarcoma, as well as hematologic malignancies, including acute myeloid leukemia, chronic lymphocytic leukemia, multiple myeloma, and lymphoma 1,5 XPO1 overexpression has been associated with poor prognosis, including being correlated with tumor grade, size, metastases, resistance to chemotherapy, as well as shorter progression-free survival (PFS) and overall survival (OS) 1 Mechanism of Action and Preclinical Rationale SL-801 is a reversible XPO1 inhibitor; Potential for improved safety profile / therapeutic window Potent preclinical in vitro and vivo activity against multiple cancer types Age, years Cancer Diagnosis n Median [range] 64 [39-76] Colorectal cancer (CRC) 5 Gender [n, (%)] Breast cancer 4 Female 18 (51) Non-small cell lung cancer (NSCLC) 3 Lines of therapy prior to the study [n, (%)]* 1 st GI adenocarcinoma (GI Adeno) 3 Line 3 (9) 2 nd Neuroendocrine (Neuro-endo) 3 Line 7 (21) 3 rd Line 6 (18) Pancreatic cancer 2 4 th Line 18 (53) Adenoid Cystic Carcinoma (ACC) 2 RAS mutation [n, (%)] Ovarian carcinoma 2 KRAS mutation: Squamous cell carcinoma (SCC) 2 Yes 5 (14) Biliary 1 No 9 (26) Renal 1 Unknown 19 (54) Bladder 1 Other mutation: 2 (6) Basal cell carcinoma (BCC) 1 ECOG performance status [n, (%)] Small bowel (28) Mesothelioma (Mesoth) 1 23 (66) (6) Leiomyosarcoma (LMS) 1 Follow-up time on study, months Appendix carcinoma 1 Median [range] 1.4 [ ] Paraganglioma 1 * One patient did not have their systemic therapy history available Safety and Tolerability Treatment Related Adverse Events (AEs) (n=35 patients) Most Common Treatment Related Adverse Events (TRAEs, 15%) All Grades n (%) TRAEs n (%) Preferred Term TRAEs All AEs G1 & 2 G3 G4 G5 Nausea 19 (54.3) 20 (57.1) 16 (45.7) 3 (8.6) Vomiting 13 (37.1) 20 (57.1) 12 (34.3) 1 (2.9) Fatigue 10 (28.6) 14 (40.0) 10 (28.6) Diarrhea 8 (22.9) 12 (34.3) 6 (17.1) 2 (5.7) Decreased appetite 7 (20.0) 10 (28.6) 7 (20.0) Treatment Duration 1 Line of Cancer Type Therapy BCC 2 SD u a Neuroendo 4+ GI Adeno 4+ SD u a Breast 4+ SD u a CRC 4+ SD u a Neuroendo 1 SD u a Small Bowel 3 u b Biliary 3 SD u a Paraganglioma 4+ u a GI Adeno 4+ SD u d SCC 3 SD u c CRC 3 u a GI Adeno 3 u a Ongoing, receiving SL-801 Breast 4+ u a In addition (not shown): SCC 3 u a 3 recently enrolled patients (10 th cohort: 60 mg) NSCLC 4+ u a are receiving SL-801, ongoing Mesothelioma 1 SD u d NSCLC 2 u a Breast 4+ u a CRC 4+ u a Ovarian u 55 mg cohort 4+ a LMS u 50 mg cohort 4+ a 45 mg cohort Pancreas 4+ u a 40 mg cohort CRC 2 u a 35 mg cohort ACC - Parotid 1 u e 30 mg cohort NSCLC 2 u a 20 mg cohort Ovarian 4+ u a 10 mg cohort Neuroendo 2 u a 5 mg cohort ACC Head & Neck 2 u d u Discontinued, disease progression Breast u a 4+ a Bladder 2 u b u b Discontinued, PI decision Pancreas 4+ u d u c Discontinued, patient death, unrelated to SL-801 CRC * u d u d Discontinued, consent withdrawn Appendix 4+ u d u e Discontinued, AE Renal 4+ u b Summary Efficacy Ideal therapeutic dose not yet determined as dose escalation continues Stable disease (SD) achieved in 26% (9/35) of patients in a heavily pretreated (71% 3rd line or greater) patient population Five patients had SD over 4+ months, including 1 BCC patient with SD over 10 months duration - 21% disease shrinkage noted in one patient with heavily pre-treated neuroendocrine tumor One additional patient (4+ prior lines of therapy) receiving SL-801 for 4+ months, ongoing Safety Manageable safety and tolerability profile observed during dose escalation No modification of dosing schedule required thus far No DLT or MTD has been reached up to 55 mg/day Most common TRAEs were grade 1-2, with no grade 4 or 5 toxicity reported Pharmacokinetics Dose-dependent increases in exposure observed Study Status Dose escalation continues, tenth cohort (60 mg/day) currently enrolling Manageable safety and tolerability profile demonstrated thus far Achievement of multiple cases of stable disease, including with tumor reductions, in some patients with heavily pre-treated solid tumors Study Design Stage 1 (Dose- escalation) - Enrollment Ongoing Stage 2 (Expansion) - Not started yet Advanced solid tumors Disease-specific cohorts (up to 4 cohorts) SL-801 orally administered - ~20 patients per cohort - Dose escalation (mg/day) SL-801 orally administered o 5, 10, 20, 30, and by 5 mg increments - Dose and regimen selected from Stage 1 thereafter Primary endpoints: - D1-4 and D8-11 of a 21-day cycle o ORR - Standard 3x3 design o Safety profile Primary endpoints: Secondary endpoints: o Safety and tolerability o CR, DoR, PFS, OS o DLT and MTD Secondary endpoints: o Pharmacokinetics o Efficacy (ORR, DCR, DoR, PFS and OS) Abbreviations: DLT = dose-limiting toxicity; ORR = overall response rate; DCR = disease control rate; DoR = duration of response; PFS = progression-free survival; OS = overall survival; MTD = maximum tolerated dose; CR = complete response TRAEs by dose level (n=35 patients) Nausea Vomiting Fatigue Diarrhea Decreased appetite Dose G N level 1-2 G3 G4 G5 Tot G 1-2 G3 G4 G5 Tot G 1-2 G3 G4 G5 Tot G 1-2 G3 G4 G5 Tot G G3 G4 G5 Tot mg mg mg mg mg mg mg mg mg Dose Dose Cohort n Cohort n (mg/day) (mg/day) enrolling No DLT s reported Dose escalation ongoing No MTD Currently enrolling 10th cohort (60 mg/day) As of 30-Apr-18. Investigator-assessed data; unaudited Additionally, there was a one grade 3 TRAE of acute kidney injury reported at 30 mg/day dose level and one grade 3 TRAE of neutropenia reported at 10 mg/day dose level Months As of April 30, Investigator-assessed data; unaudited. 1 Time from C1D1 to end of treatment or ongoing * One patient did not have their systemic therapy history available Representative Patient CT Scans Representative target lesion response 74 year old female with metastatic stage IV basal cell carcinoma (BCC) in the head and neck region. Prior therapies included vismodegib and an experimental anti-cd40 therapy Achieved stable disease (SD) while receiving SL-801; CT scans (day 21 of cycle 2 vs baseline) indicated a reduction in target lesions of 14% (47.5 à 41 mm) Durable SD for 14 cycles Takeaways and Next Steps Phase 1 trial of SL-801, a novel XPO1 inhibitor, in heavily pre-treated patients with solid tumors Manageable safety and tolerability profile, largely grade 1-2 adverse events (AEs), to date No dose limiting toxicity (DLT) or maximum tolerated dose (MTD) reached Dose escalation ongoing; 10 th cohort (60 mg/day) currently enrolling Multiple cases of stable disease (SD) in a heavily pretreated solid tumor patient population Pharmacokinetic (PK) analyses suggest dose-dependent increases in exposure; studies ongoing Ideal therapeutic dose not yet determined as dose escalation continues Further updates expected this year Given favorable data profile thus far with SL-801, coupled with clinical validation of the XPO1 target, additional SL-801 trials, including in hematologic cancers and combination studies, planned References 1. Turner et al. Biochemical pharmacology 2012; 83(3): Tan et al. American journal of physiology Renal physiology 2014; 307(11): F Siddiqui et al. WIREs RNA 2012; 3: Hung et al. Journal of cell science 2011; 124(Pt 20): Senapedis et al. Seminars in cancer biology 2014; 27:74-86 Disclosures: Qi: Stemline - employment, equity ownership; Olguin: Stemline - employment, equity ownership; Bullington: Stemline - employment, equity ownership; Sardone: Stemline - employment, equity ownership; Dunn: Stemline - employment, equity ownership; Shemesh: Stemline - employment, equity ownership; Chen: Stemline - employment, equity ownership; Brooks: Stemline - employment, equity ownership Disclaimer: Copies of this poster obtained through Quick Response (QR) Code are for personal use only and may not be reproduced without permission from ASCO and the author of this poster.

38 SL-701

39 IL-13Ra2 Survivin EphA2 39 SL-701: Background SL-701 is an off-the-shelf, systemically-delivered (subcutaneous) immunotherapy Short synthetic peptides, some mutated, to generate antigen specific CD8 + T cell response - Co-administered with immunostimulants Targets (IL-13Ra2, Ephrin A2, Survivin) over-expressed on glioblastoma (GBM) Overexpression of SL-701 targets on GBM Normal brain GBM targets: IL-13Ra2, Survivin, Ephrin A2 GBM Mechanism of Action Directs T cells to GBM T cell response/inflammation in brain biopsy post-systemic therapy (earlier version of SL-701) Abundant CD8 + T cells Numerous CD68 + macrophages Adapted from Uematsu, MJ. Neurooncol, 2005 and Wykosky, J. Clin Cancer Res, 2008 JCO, 2011; ASCO, 2011

40 SL-701: Phase 2 Trial Design and Demographics SL-701: Phase 2 Trial Design (STML ) Stage 1 (single agent) SL-701, with immunostimulants (GM-CSF + imiquimod) Eligibility: Second-line GBM Stage 1 Stage 2 (Combination) SL bevacizumab, with immunostimulants (poly-iclc) Eligibility: Second-line GBM Stage 2 SL-701 GM-CSF + Imiquimod MRI MRI SL-701 poly-iclc Bevacizumab MRI MRI Week: Week: *Previous ISTs (~70+ patients) with earlier version of SL-701, multiple administration regimens/schedules, demonstrated tolerability with activity (major responses) in some adults and children with malignant high grade Stage gliomas, 2 including GBM and pediatric brainstem non -brain stem gliomas Eligibility: Second-line GBM After week 22: SL-701 / GM-CSF / imiquimod every 4 weeks thereafter until disease progression After week 22: SL-701 / poly-iclc every 4 weeks and bevacizumab (as per label) every 2 weeks thereafter until disease progression SL-701 poly-iclc Stage 1 Stage 2 Total Stage 1 Stage 2 Total Bevacizumab (n=46) (n=28) (n=74) (n=46) (n=28) (n=74) Age, years Median Week: [range] 0 2 MRI 54 [24-72] [26-79] [24-79] 12 Disease related MRI genotype MGMT 14 promoter 16 18methylation status: Gender [n, (%)] Methylated / Hypermethylated 7 (15.2) 10 (35.7) 17 (23.0) Male 30 (65.2) 18 (64.3) 48 (64.9) KPS score at screening [n, (%)] (13.0) 5 (17.9) 11 (14.9) (50.0) 8 (28.6) 31 (41.9) (28.3) 9 (32.1) 22 (29.7) 70 4 (8.7) 6 (21.4) 10 (13.5) Follow-up time, months Median [range] 10.9 [ ] After week 22: SL-701 / poly-iclc every 4 weeks and bevacizumab (as per label) every 2 weeks thereafter until disease progression 10.8 [ ] [ ] Unmethylated 9 (19.6) 10 (35.7) 19 (25.7) Unknown 30 (65.2) 8 (28.6) 38 (51.3) IDH1 mutation status: Mutation present 2 (4.3) 2 (7.1) 4 (5.4) No mutation 16 (34.8) 17 (60.7) 33 (44.6) Unknown 28 (60.9) 9 (32.1) 37 (50.0) 40 Stage 1 Stage 2 Total (n=46) (n=28) (n=74) Surgery at recurrence [n, (%)] Complete resection 26 (56.5) 20 (71.4) 46 (62.2) Partial resection 16 (34.8) 7 (25.0) 23 (31.1) No surgery at recurrence 4 (8.7) 1 (3.6) 5 (6.7) Prior GBM anti-cancer therapies [n, (%)] TMZ based therapy 40 (86.9) 26 (92.9) 66 (89.2) Gliadel wafer 1 (2.2) 0 1 (1.4) Investigational agent / Other 3 (6.5) 2 (7.1) 5 (6.7) Not specified 2 (4.3) 0 2 (2.7)

41 41 Disease Control, Including Major Responses Modified RANO Criteria (ITT) Stage 1 Stage 2 n (evaluable/total) 46/46 28/28 Disease Control Rate (DCR) 1, n (rate) Objective Response Rate (ORR) 2, n (rate) 10 (22%) (95% CI: 10.9, 36.4) 1 (2%) (95% CI: 0.1, 13.2) 15 (54%) (95% CI: 33.9, 72.5) 4 (14%) (95% CI: 4.0, 32.7) Complete response (CR), n (rate) 0 (0%) 2 (7%) Partial Response (PR), n (rate) 1 (2%) 2 (7%) Stable Disease (SD), n (rate) 13 (28%) 22 (79%) RANO = Revised Assessment in Neuro-Oncology; ITT = intent to treat; CI = confidence interval 1 DCR is the proportion of patients who have a best response of CR, PR or SD documented on 2 consecutive MRIs 4 weeks apart as judged by modified RANO criteria. 2 ORR is the proportion of patients who have a best response of CR or PR documented on 2 consecutive MRIs 4 weeks apart as judged by modified RANO criteria.

42 Overall Survival (OS) Stage 1 Overall Survival Stage 1, N=46 Stage 2 Overall Survival Stage 2, N=28 Survival Probability % 12-month OS (OS-12) Survival Probability % 12-month OS (OS-12) Time (months) OS-12 = 44% (95% CI: 28.9, 58.9) Median OS = 11.0 months (95% CI: 8.2, 12.0) Time (months) OS-12 = 50% (95% CI: 30.6, 69.4) Median OS = 11.7 months (95% CI: 7.1, NE) Above calculations by Clopper-Pearson method NE = not estimable Historical OS-12: ~20-38% in trials of bevacizumab in patients with recurrent GBM (BRAIN, ReACT control arm, BELOB, CABARET, and NCI 64E) 1 1 References: BELOB: Taal et. al., Lancet Oncol 2014; BRAIN: Friedman et. al., JCO 2009; ReACT: Celldex Presentation; CARBARET: Field et. al., Neuro Oncol. 2015; NCI 64E FDA Briefing Documents 42

43 43 Target-Specific CD8+ T Cell Immunophenotyping by Flow Cytometry Frequency of antigen-specific CD8+ T cells (%) Potential immune-related biomarker 0.0

44 44 Long-Term Survivors Comprised Largely of Target-Specific CD8+ T Cell Responders Overall Survival Stage Stage 2, N=28 2 (All patients) Stage 2 (Target-Specific CD8+ N=8T cell Responders) Survival Probability Tail comprised largely of patients with Target-Specific T cell Response Survival Probability % OS-12 Median OS not reached Target-Specific CD8 + T cell Responders Target-Specific CD8 + T cell Responders Time (months) Time (months)

45 Complete Responses (CRs) and High Target-Specific CD8+ T cell Responses Patient Narrative 60 year-old male Grade IV GBM, KPS 90%, MGMT promoter methylated, non-mutated IDH1 Prior treatment: 1 resections + Stupp + Veliparib Received SL bevacizumab - CR after 4 months - Confirmed by 2 nd assessment Target-specific CD8+ T cells CR Pre-SL months of SL months of SL months of SL

46 Complete Responses (CRs) and High Target-Specific CD8+ T cell Responses Patient Narrative 51 year-old male Grade IV GBM, KPS 90%, MGMT promoter methylated Prior treatment: 2 resections + Stupp Received SL bevacizumab - PR after 2 months, confirmed by 2nd assessment - Subsequently converted to CR, confirmed by 2nd assessment CR PR Target-specific CD8+ T cells Pre-SL months of SL

47 47 Conclusions and Next Steps Long-term survivors: 50% 12-month OS with SL bevacizumab Long-term survivors comprised largely of patients with target-specific CD8+ T-cell responses 75% 12-month OS, median OS not reached Indicates potential correlation of immune-related biomarker with clinical outcome Major responses, including CRs, and durable stable diseases in second-line GBM Well-tolerated, very manageable side effect profile Given the major unmet medical need in GBM and promising safety and efficacy data generated to date with SL-701, Stemline is considering next steps to unlock value including leveraging potential immune-related biomarker in registration-directed trial designs

48 Milestones

49 49 Program Milestone Estimated Timeframe ELZONRIS BPDCN ELZONRIS Additional indications Other pipeline candidates Pre-BLA meeting Agreement with FDA on rolling BLA submission Hire commercial leadership team including Head of Sales and Head of Reimbursement & Access Disease awareness campaign and market shaping operational plan launched Complete submission of rolling BLA Acceptance of BLA by FDA EMA pre-maa meeting 2H18 PDUFA Date February 21, 2019 Potential MAA filing (EU) Data presentations at scientific meetings Milestones Formulate registrational strategy (CMML and/or MF) Initiate pivotal trial in additional indication(s) SL-801: Data presentation at scientific meetings SL-701: Data presentation at scientific meetings 1H19 Mid-18 and 2H18 4Q18-1Q19 2H19 Mid-18 and 2H18 Mid-18 and 2H18

50 Financial Summary

51 51 Financial Summary As of June 30, 2018 Cash, Cash Equivalents and Investments (MM) $97.1 Debt $0.0 Shares Outstanding (MM) 30.9

52 Stemline Therapeutics, Inc. NASDAQ: STML Corporate Presentation August 2018