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Stemline Therapeutics, Inc. NASDAQ: STML Corporate Presentation January 2018

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. 2

Investment Highlights Goal is to become a leading commercial stage biotechnology company CD123-targeting represents multi-billion dollar market opportunity BLA submission and possible approval in first CD123 + indication this year Clinical activity in second and third CD123+ indications Pursuing additional indications, including all-comer CD123 trial BPDCN Universe Hematologic Cancers Solid Cancers Autoimmune Abbreviations: BPDCN = blastic plasmacytoid dendritic cell neoplasm 3

Clinical Programs

Stemline Clinical Programs Additional Clinical Candidates Lead Clinical Program SL-401 Targeted therapy directed to IL-3R (CD123) Breakthrough Therapy Designation (BTD) Pivotal trial in BPDCN met primary endpoint Ramping up pre-launch activities SL-801 XPO-1 inhibitor Phase 1 trial in advanced solid tumors Dose escalation ongoing 5 SL-701 Immunotherapy Phase 2 trial completed in 2nd-line GBM Patient follow-up ongoing

Stemline Clinical Pipeline Program Target Indication IND Phase 1 Phase 2 BPDCN SL-401 single agent (Pivotal) Enrollment completed 1 MPN (CMML and MF) SL-401 single agent Enrolling SL-401 IL-3R (CD123) AML (in CR, MRD+) Myeloma (r/r) SL-401 single agent SL-401 + pomalidomide + dex Enrolling Enrolling High risk MDS, Elderly AML SL-401 + 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 = myleoproliferative 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 Stage 3 enrollment completed. To ensure continued patient access, Stemline is enrolling first-line and r/r BPDCN patients under the current protocol (Stage 4). 6

SL-401: BPDCN

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 2008 - 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 2012. 8 CD4 CD56 TCL1 CD123

SL-401 Pivotal Trial Results

Study Design and Inclusion / Exclusion ASH 17 Stage 1 (Lead-in, dose escalation) BPDCN (1L and R/R) ǂ SL-401 (7, 9, 12, or 16 µg/kg) via IV infusion, days 1-5 of a 21- day cycle Key objectives: determine optimal dose and regimen for Stage 2 Stage 2 (Expansion) BPDCN (1L and R/R) SL-401 (12 µg/kg) via IV infusion, days 1-5 of a 21-day cycle Key objectives: further define safety and efficacy BPDCN (1L) Stage 3 (Pivotal, confirmatory) SL-401 (12 µg/kg) via IV infusion, days 1-5 of a 21-day cycle Key objectives: efficacy confirmation for registration Select inclusion criteria Patient Population: - Stage 1: BPDCN (1L or R/R) - Stage 2: BPDCN (1L or R/R) - Stage 3: BPDCN (1L) Age 18; ECOG PS 0-2 Adequate organ function including: LVEF lower limit of normal, creatinine 1.5mg/dL, albumin 3.2 g/dl, bilirubin 1.5 mg/dl, AST/ALT 2.5x ULN Select exclusion criteria Persistent clinically significant toxicities from prior chemotherapy Received chemotherapy or other investigational therapy within the prior 14 days Clinically significant cardiopulmonary disease Receiving immunosuppressive therapy To ensure ongoing access to SL-401, BPDCN patients are being enrolled in an additional cohort, Stage 4 ǂ Stage 1 also enrolled AML (R/R) patients, to be reported separately In BPDCN, 12 µg/kg/day was highest tested dose (MTD not reached) and selected for Stage 2 Abbreviations: 1L = first-line; R/R = relapsed/refractory; IV = intravenous; ECOG PS = Eastern Cooperative Oncology Group performance status; LVEF = left ventricular ejection fraction; ULN = upper limit of normal; MTD = maximum tolerated dose 10

Clinical Activity Stage 3 ASH 17 Stage 3: BPDCN (12 µg/kg/day) (n=13 patients) Stage 3 was designed to serve as the pivotal, confirmatory cohort for the SL-401 trial in BPDCN Stage 3 met its primary endpoint with a 54% rate of CR + CRc (7/13) [95% CI: 25.1, 80.8] - The lower bound of the 95% CI exceeded the pre-specified rate of 10% Stage 3 responders ɸ Line of Therapy First-line Dose Level 12 µg/kg n 13 ORR, n (%) 10 (77%) CR + CRc + CRi, n (%) 7 (54%) CR 3 CRc 4 CRi 0 PR, n (%) 3 (23%) Bridged to SCT, n (%) 6 (46%) Allo 6 Auto 0 Stage 3 complete responders ɸ Age (years) Best Response Bone Marrow (% Blasts) Baseline Best response Baseline Skin (mswat) Best response SCT RFS (months) 69 CR 94% 2% 1.2% 0.0% Allo 6.4 + 68 CRc 70% 2% 72.0% 0.0% Allo 6.0 + 57 CR 66% 2% 35.0% 0.0% Allo 5.5 + 74 CRc 22% 1% 54.0% 4.0% - 7.3 65 CR 12% 1% 70.0% 0.0% Allo 7.5 + 32 CRc 2% 2% 18.0% 0.3% Allo 8.3 + 22 CRc 1% 1% 22.0% 0.4% Allo 5.3 + ɸ As of September 25, 2017. Investigator-assessed. ɣ In addition, in Stage 1 (lead-in, dose escalation), 3 BPDCN patients received SL-401 at 7µg/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 gross reduction in cutaneous lesions and residual microscopic skin disease; 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. 11

Clinical Activity (Stages 1, 2, and 3) ASH 17 Stages 1, 2, and 3 responders ɸ,ɣ Stages 1, 2, and 3: BPDCN (12 µg/kg/day) (n=42 patients) Line of Therapy 1L R/R 1L & R/R n 29 13 42 ORR, n (%) 26 (90%) 9 (69%) 35 (83%) CR + CRc + CRi, n (%) 21 (72%) 5 (38%) 26 (62%) CR 12 1 13 CRc 7 3 10 CRi 2 1 3 PR, n (%) 5 (17%) 4 (31%) 9 (21%) Bridged to SCT, n (%) 13 (45%) 1 (8%) 14 (33%) Allo 10 1 11 Auto 3 0 3 ɸ As of September 25, 2017. Investigator-assessed. ɣ In addition, in Stage 1 (lead-in, dose escalation), 3 BPDCN patients received SL-401 at 7µg/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 gross reduction in cutaneous lesions and residual microscopic skin disease; 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. 12

Safety and Tolerability ASH 17 All SL-401 Clinical Trials (12 µg/kg/day) (n=114 patients) Preferred Term Most Common Adverse Events (AEs) (>15% treatment-related AEs, TRAEs) ƾ All Grades n (%) TRAEs n (%) TRAEs All AEs Grade 1-2 Grade 3 Grade 4 Grade 5 Hypoalbuminaemia 56 (49%) 62 (54%) 55 (48%) 1 (1%) 0 (0%) 0 (0%) Alanine aminotransferase increased 55 (48%) 65 (57%) 25 (22%) 30 (26%) 0 (0%) 0 (0%) Aspartate aminotransferase increased 55 (48%) 63 (55%) 24 (21%) 27 (24%) 4 (4%) 0 (0%) Thrombocytopenia Ж 33 (29%) 42 (37%) 7 (6%) 6 (5%) 20 (18%) 0 (0%) Nausea 31 (27%) 58 (51%) 31 (27%) 0 (0%) 0 (0%) 0 (0%) Pyrexia 29 (25%) 49 (43%) 29 (25%) 0 (0%) 0 (0%) 0 (0%) Chills 26 (23%) 38 (33%) 25 (22%) 1 (1%) 0 (0%) 0 (0%) Fatigue 26 (23%) 57 (50%) 22 (19%) 4 (4%) 0 (0%) 0 (0%) Capillary leak syndrome (CLS) ђ 23 (20%) 23 (20%) 15 (13%) 5 (4%) 2 (2%) 1 (1%) Weight increased 22 (19%) 33 (29%) 22 (19%) 0 (0%) 0 (0%) 0 (0%) Hypotension 20 (18%) 33 (29%) 17 (15%) 3 (3%) 0 (0%) 0 (0%) Oedema peripheral 19 (17%) 50 (44%) 18 (16%) 1 (1%) 0 (0%) 0 (0%) Vomiting 17 (15%) 30 (26%) 17 (15%) 0 (0%) 0 (0%) 0 (0%) ƾ As of October 18, 2017. Ж Includes low platelets and platelets decreased. ђ An additional grade 5 CLS-related event occurred in one Stage 4 BPDCN patient (of 11 enrolled) which, in addition to two previously reported grade 5 CLS-related events that occurred at 7 µg/kg/day (BPDCN) and 16 µg/kg/day (AML), reflects a rate of 2.6% (4/153) for all trials and doses, and a rate of 1.7% (2/119) for all trials at the 12 µg/kg/day dose as of 11-21-17 13

Bone Marrow Responses ASH 17 14

Best Response and Treatment Duration ASH 17 Stages 1 and 2: First-line BPDCN (12 µg/kg/day) Stage 3: First-line BPDCN (12 µg/kg/day) Individual patients 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 CR CR CRc CR PR CR CR CR CRc CR CRi CRc PR CRi CR CR Allo Auto Auto Allo Allo Allo u SL-401 Stem cell transplant (SCT) Receiving SL-401, ongoing Auto u 29 28 27 26 25 24 23 22 21 20 19 18 17 CRc CR CR CR CRc CRc CRc PR PR SD SD PR Allo Allo Allo Allo Allo Allo SL-401 Stem cell transplant (SCT) Exited study in remission 0 8 15 23 30 Time (Months) As of September 25, 2017. Investigator-assessed. 15 0 3 5 8 10 Time (Months) As of September 25, 2017. Investigator-assessed. Patient relapsed off study at 7.3 months.

Overall Survival (OS) ASH 17 First-line BPDCN (12 µg/kg/day) Stage 1 and 2 OS (from first dose) Stage 3 OS (from first dose) 16

SL-401: BPDCN Market Opportunity

SL-401: Multiple Opportunities for Growth within BPDCN Universe BPDCN (EU) BPDCN Signature Maintenance Therapy (post-sct) BPDCN (US) 18

SL-401: Multiple Opportunities for Growth within BPDCN Universe BPDCN (EU) BPDCN Signature Maintenance Therapy (post-sct) BPDCN (US) ~40% first-line BPDCN patients on SL-401 bridged to SCT Study Design In Process 19

SL-401: Multiple Opportunities for Growth within BPDCN Universe BPDCN Signature (30%) x (16%) x new AML cases (EHA, 2016) Potential upside 20

SL-401: 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) ~40% first-line BPDCN patients on SL-401 bridged to SCT Study Design In Process 21

BPDCN Awareness Highlighting Utility of CD123 Testing 22

SL-401: Market Expansion Opportunities

SL-401: Additional Opportunities SL-401 across multiple indications Both single agent and in combination; various administration schedules MPN (CMML, MF) AML in CR, MRD + Multiple myeloma (r/r) High risk MDS or elderly AML unfit for chemo Regimen SL-401 SL-401 SL-401 + Pomalidomide* SL-401 + Azacytidine* Lead-in (Stage 1) Completed Completed Enrolling Enrolling Expansion (Stage 2) Enrolling Enrolling Not started yet Not started yet Dose and Schedule 12 ug/kg/day (3 days every 3-4 wks) 12 ug/kg/day (5 days every 4 wks) Optimal dose and schedule TBD Optimal dose and schedule TBD Efficacy readout ORR CR rate MRD decrease DFS pdc decrease ORR CR rate *Preclinical data support combination (synergy or potentiation) 24

SL-401: Results from Ongoing Phase 1/2 Trial in Myeloproliferative Neoplasms Including CMML and MF

SL-401 MPN Phase 1/2 Trial ASH 17 Study Design Demographics Safety and Tolerability Stage 1 Lead-in (Completed) MPN: CMML, MF, SM, and PED SL-401 (7, 9, or 12 µg/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: determine optimal dose and regimen for Stage 2 Stage 2 Expansion ( Enrolling) MPN: CMML or MF without evidence of transformation SL-401 (12 µg/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: further define safety and efficacy Age, years n = 24 Median [range] 69 [43 81] Gender Male 13 (54) MPN MF 12 (50) CMML-1 7 (29) CMML-2 4 (17) SM 1 (4) Median ECOG Median ECOG [range] 1 [0-2] Median Blast Count, % Median [range] 5 [0-15] Prior lines of treatment [n, (%)] Prior SCT 3 (12) JAKi 9 (38) HMA 7 (29) Baseline sites of disease [n, (%)] BM 13 (63) Spleen 17 (75) Liver 5 (21) Enrollment by Stage (dose) Stage 1 (7, 9, 12 µg/kg) 9 (3, 3, 3) Stage 2 (12 µg/kg) 15 27 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 7 (33.3) 8 (38.1) 7 (33.3) -- -- -- Thrombocytopenia 7 (33.3) 8 (38.1) 2 (9.5) 4 (19.0) 1 (4.8) -- Fatigue 6 (28.6) 11 (52.4) 5 (23.8) 1 (4.8) -- -- Alanine aminotransferase increased 5 (23.8) 6 (28.6) 4 (19.0) 1 (4.8) -- -- Anemia 5 (23.8) 10 (47.6) 1 (4.8) 4 (19.0) -- -- Capillary leak syndrome (CLS) 5 (23.8) 5 (23.8) 4 (19.0) 1 (4.8) -- -- Oedema peripheral 5 (23.8) 13 (61.9) 5 (23.8) -- -- -- Nausea 4 (19.0) 10 (47.6) 4 (19.0) -- -- -- Vomiting 4 (19.0) 8 (38.1) 4 (19.0) -- -- -- As of October 25, 2017. Detailed Safety assessments on three patients are pending Includes low platelets and platelets decreased

SL-401 MPN Trial: Best Spleen Response ASH 17 Splenomegaly (cm palpable below left costal margin) Patient Dose Received (µg/kg) Histology Overall Best Response Screening Best Response Percent Change Time to response (weeks) 6 9 CMML-1 CR 5 0 100% 1.7 9 12 CMML-1 2 0 100% 14.7 3 7 CMML-2 SD 20 10 50% 4.1 7 12 MF SD 35 19 46% 12.1 1 7 MF 30 20 33% 4.7 18 12 MF SD 5 0 100% 3 22 12 CMML-2 2 0 100% 8 23 12 CMML-1 4 0 100% 3.9 15 12 MF SD 19 10 47% 33.7 21 12 CMML-2 22 14 36% 2.7 12 12 MF SD 14 10 29% 11 10 12 CMML-1 14 13 7% 7.9 Stage 1 Stage 2 Abbreviations: CR = Complete response; SD = Stable disease 28

MPN: Best Response, Treatment Duration / Summary and Next Steps ASH 17 SL-401 Trial in MPN (CMML and MF) Safety No DLTs or MTD identified. Most common TRAEs include hypoalbuminemia (33%), thrombocytopenia (33%), and fatigue (29%). Most common TRAEs, grade 3+, include thrombocytopenia (24%) and anemia (19%) Efficacy Durable CR (14+ months) noted in CMML patient 65% (11/17 evaluable) CMML and MF patients had spleen reductions >25% (range 29% to 100%) Durable SD in 4 patients (2 CMML, 2 MF) for 5+ to 8+ months, 3 ongoing All 3 ongoing patients had baseline platelet counts <100,000, including 1 patient platelet count <50,000 Next Steps Continue enrollment and patient follow-up Favorable tolerability and preliminary signs of activity support both single agent and combination development strategies, including JAK-inhibitors and hypomethylating agents 29

Key Accomplishments and Upcoming Milestone Events 2017 Timing Program Expected Event 1Q17 SL-401 Completed enrollment of BPDCN pivotal trial 2Q17 SL-401 Clinical update in BPDCN at EHA 2H17 SL-401 Top-line pivotal data ASH 17 SL-401 Detailed pivotal data ASH 17 SL-401 Updates on additional indications 2018 Timing Program Expected Event 1H18 SL-401 BLA submission Mid-18 SL-401 Commercial build-out, hire salesforce 2H18 SL-401 EMA pre-filing meeting 2H18 SL-401 Potential US approval 2H18 SL-401 Formulate registration strategy for additional indication(s) 2H18 SL-401 Updates on ongoing and new clinical trials 30

SL-801

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 ESMO 2017 Dose escalation; enrollment ongoing 32

SL-801: Rationale XPO1 inhibition may be a promising therapeutic strategy in certain KRAS-mutant cancers 33

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 Ø 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 34

SL-801: Patient demographics (n=24) ESMO 17 Age, years Median [range] 64 [39-76] Gender [n, (%)] Male 13 (54) Lines of therapy prior to the study [n, (%)] 1 st Line 1 (4) 2 nd Line 5 (22) 3 rd Line 18 (74) KRAS mutation [n, (%)] Yes 4 (16.6) No 7 (29) Unknown 13 (54) ECOG performance status [n, (%)] 0 6 (25) 1 17 (71) 2 1 (4) Follow-up time on study, months Median [range] 1.4 [0.2 4.9] Cancer Diagnosis n Colorectal cancer (CRC) 5 Breast cancer 3 Non-small cell lung cancer (NSCLC) 2 GI adenocarcinoma (GI Adeno) 2 Pancreatic cancer 2 Neuroendocrine (Neuro-endo) 2 Biliary 1 Renal 1 Bladder 1 Ovarian carcinoma 1 Basal cell carcinoma (BCC) 1 Small bowel 1 Mesothelioma (Mesoth) 1 Anal squamous cell carcinoma (SCC) 1 *As of 31-Jul-2017. Investigator-assessed data; unaudited. 35

SL-801: Safety and Tolerability ESMO 17 Treatment Related Adverse events (AEs) (n= 24 patients) Most Common Treatment Related Adverse Events ( 15%) All Grades n (%) TRAEs n (%) Preferred Term TRAEs All AEs G1 & 2 G3 G4 G5 Nausea 10 (41.7) 14 (58.3) 9 (37.5) 1 (4.2) -- -- No DLT s reported No MTD Dose escalation ongoing Ø Enrolling 8 th cohort (50 mg/day) Fatigue 7 (29.2) 10 (41.7) 7 (29.2) -- -- -- Diarrhea 5 (20.9) 8 (33.3) 4 (16.7) 1 (4.2) -- -- Vomiting 4 (16.7) 10 (41.7) 4 (16.7) -- -- -- Decreased appetite 4 (16.7) 7 (29.2) 4 (16.7) -- -- -- *As of 31-Jul-2017. Investigator-assessed data; unaudited. There was also one grade 3 TRAE of acute kidney injury reported at 30 mg/day dose level 36

SL-801: Clinical Activity ESMO 17 Sum of target lesions (measurable) Dose Tumor Histology No. of lesions Screening (mm) Best Response (mm) % Δ of target lesions Overall response assessment Time to Best Response Last dose received Remains on Therapy 30 mg Neuro-endo 2 44 35-20.5% SD C2 C6D1 No 30 mg GI Adeno 2 40 34-15.0% SD C4 C7D1 No 40 mg BCC 1 47.5 41-13.7% SD C2 C3D11 Yes 40 mg Breast 5 193 184-4.7% SD C2 C2D1 Yes 5 mg CRC 1 3 76 74-2.6% SD C2 C6D1 No 10 mg Anal SCC 2 38 38 0 SD C2 C4D1 No 40 mg Mesoth 3 70 71 +1.4% SD C2 C2D1 No 20 mg Breast 3 195 206 +5.6% SD C2 C2D1 No *As of 31-Jul-2017. Investigator-assessed data; unaudited. (-) = reduction; (+) = increase; SD = stable disease 1 Patient with KRAS mutation present at screening An additional patient (cholangiocarcoma), not shown, sustained SD on SL-801 (35mg cohort); data on tumor size pending 37

SL-801: Trial Status and Next Steps Next Steps Dose escalation continues - 8 th cohort (50 mg/day) currently enrolling Further efficacy and safety updates expected 2018 Additional trials planned include single agent, combination, and hematologic cancers 38

SL-701

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) GBM targets: Mechanism of Action Directs T cells to GBM IL-13Ra2 IL-13Ra2, Survivin, Ephrin A2 Overexpression of SL-701 targets on GBM Normal brain GBM T cell response/inflammation in brain biopsy post-systemic therapy (earlier version of SL-701) Abundant CD8 + T cells Survivin EphA2 Adapted from Uematsu, MJ. Neurooncol, 2005 and Wykosky, J. Clin Cancer Res, 2008 Numerous CD68 + macrophages JCO, 2011; ASCO, 2011 40

SL-701: Treatment Related Adverse Events ( 5%) (n=74) SNO 17 Preferred Term All Grades n (%) TRAEs n (%) TRAEs All AEs Grade 3 Fatigue 16 (21.6) 29 (39.2) 2 (2.7) 1 Injection site reaction 13 (17.6) 15 (20.3) -- Injection site erythema 9 (12.2) 11 (14.9) -- Injection site pain 8 (10.8) 9 (12.2) -- Injection site induration 6 (8.1) 8 (17.4) -- Headache 6 (8.1) 24 (32.4) -- Nausea 5 (6.8) 15 (20.3) -- Injection site swelling 5 (6.8) 4 (8.7) -- Skin induration 5 (6.8) 3 (6.5) -- Chills 4 (5.4) 3 (6.5) -- 1 Both cases were Grade 3 41

SL-701: Disease Control and Duration of Response SNO 17 Disease Control, Including Major Responses Stage 1 Stage 2 n (evaluable/total) 46/46 28/28 Disease control 1, n (rate; DCR) 16 (35%) 27 (96%) Overall response, n (rate; ORR) 1 (2%) 6 (21%) Complete response (CR), n (rate) 0 (0%) 2 (7%) Partial Response (PR), n (rate) 1 (2%) 4 (14%) Stable Disease (SD), n (rate) 15 (33%) 21 (75%) Major responses and durable stable diseases in 2nd-line GBM As both a single agent and in combination with bevacizumab Stage 1: Duration of Response or 6 Mo SD 6.1 27.8 months (n=46) Stage 2: Duration of Response or 6 Mo SD 2.7 12.4 months (n=28) 1 Disease control = CR + PR + SD 42

SL-701: Overall Survival (OS) SNO 17 Stage 1 (n=46) Stage 2 (n=28) OS-12: 36% Median OS = 10.9 months OS-12: 48% Median OS = 11.7 months OS-12 = Overall Survival at 12 months 43

SL-701: Clinical Benefit and Robust Immune Response SNO 17 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-701 + bevacizumab - CR after 4 months - Confirmed by 2 nd assessment Target-specific CD8+ T cells CR Pre-SL-701 2 months of SL-701 9 months of SL-701 11 months of SL-701 44

SL-701: Conclusions and Next Steps Major responses and durable stable diseases with SL-701 alone and in combination with bevacizumab in second-line GBM Well-tolerated, very manageable side effect profile Long-term survivors with SL-701 alone (Stage 1) and in combination with bevacizumab (Stage 2), including ~48% 12-month OS survival probability in Stage 2 Robust target-specific CD8 + T-cell responses in patients experiencing clinical benefit consistent with mechanism of action 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 including possible registration-directed trial designs 45

Upcoming Milestones

Key Accomplishments and Upcoming Milestone Events 2017 2018 Timing Program Expected Event 1Q17 SL-401 Completed enrollment of BPDCN pivotal trial 2Q17 SL-401 Clinical update in BPDCN at EHA ESMO 17 SL-801 Phase 1 update 2H17 SL-401 Top-line pivotal data SNO 17 SL-701 Patient follow-up update ASH 17 SL-401 Detailed pivotal data ASH 17 SL-401 Updates on additional indications Timing Program Expected Event 1H18 SL-401 BLA submission Mid-18 SL-401 Commercial build-out, hire salesforce 2H18 SL-401 EMA pre-filing meeting 2H18 SL-401 Potential US approval 2H18 SL-401 Formulate registration strategy for additional indication(s) 2H18 SL-801 Further trial and program updates 2H18 SL-701 Further program updates 2H18 SL-401 Updates on ongoing and new clinical trials 47

Financial Summary

Financial Summary As of September 30, 2017 Cash, Cash Equivalents and Investments (MM) $79.9 Debt $0.0 Shares Outstanding (MM) ~25.3 49

Stemline Therapeutics, Inc. NASDAQ: STML Corporate Presentation January 2018