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Potential to add third clinical-stage program to oncology pipeline Progressing patient enrolment towards interim analyses in lisavanbulin phase 2 study and in patient cohorts in FIDES-01 and FIDES-02 studies with derazantinib Basel, Switzerland, November 16, 2021 Basilea Pharmaceutica Ltd. (SIX: BSLN), a commercial-stage biopharmaceutical company committed to meeting the needs of patients with cancer and infectious diseases, announced today that it has submitted an Investigational New Drug (IND) application to the U.S. Food and Drug Administration (FDA), to start clinical studies with the company’s novel drug candidate BAL0891 in cancer therapy. BAL0891 is a potential first-in-class small-molecule kinase inhibitor. If the IND is granted, Basilea plans to initiate a phase 1 study in patients with advanced solid tumors in the first quarter of 2022. Dr. Laurenz Kellenberger, Chief Scientific Officer said: “We are very pleased with the progress made in the project. Submitting this IND is an important regulatory milestone for Basilea as we are moving closer to adding BAL0891 as the third oncology drug candidate to our clinical pipeline.” The two oncology drug candidates already in clinical development are derazantinib, an inhibitor of the fibroblast growth factor receptor (FGFR) family of kinases, which is currently in clinical studies for the treatment of bile duct (iCCA), urothelial and gastric cancers (the FIDES studies), and lisavanbulin, a tumor checkpoint controller, currently in clinical studies with patients with glioblastoma, the most aggressive primary brain cancer. Dr. Marc Engelhardt, Chief Medical Officer, said: “We are expecting to complete enrolment of the number of patients required to support interim analyses in three oncology studies around year-end. This is the phase 2 study with lisavanbulin in glioblastoma patients whose tumors tested positive on the potentially response-predictive biomarker EB1. For derazantinib, this is the cohort of patients with urothelial cancer refractory to prior FGFR inhibitors in the FIDES-02 study and the cohort of patients with intrahepatic cholangiocarcinoma, or iCCA, with non-fusion FGFR2 genetic aberrations in the FIDES-01 study. With enrolment progressing, we now have more visibility on the timelines and expect that interim data read-outs will become available over the course of the first half of 2022.“ About BAL0891 BAL0891 is a potential first-in-class small-molecule kinase inhibitor, which was in-licensed in 2018. The compound has shown anti-proliferative activity across diverse tumor cell lines in vitro and efficacy in in-vivo models of human cancers. Basilea has filed an Investigational New Drug application to the U.S. Food and Drug Administration, with the goal to initiate first-in-human clinical studies in the first quarter of 2022. About derazantinib Derazantinib is an investigational orally administered small-molecule FGFR inhibitor with strong activity against FGFR1, 2, and 3.1 FGFR kinases are key drivers of cell proliferation, differentiation and migration. FGFR genetic aberrations, e.g. gene fusions, mutations or amplifications, have been identified as potentially important therapeutic targets for various cancers, including intrahepatic cholangiocarcinoma (iCCA), urothelial, breast, gastric and lung cancers.2 In these cancers, FGFR genetic aberrations are found in a range of 5% to 30%.3 Derazantinib also inhibits the colony-stimulating-factor-1-receptor kinase (CSF1R).1, 4 CSF1R-mediated signaling is important for the maintenance of tumor-promoting macrophages and therefore has been identified as a potential target for anti-cancer drugs.5 Pre-clinical data has shown that tumor macrophage depletion through CSF1R blockade renders tumors more responsive to T-cell checkpoint immunotherapy, including approaches targeting PD-L1/PD-1.6, 7 Derazantinib has demonstrated antitumor activity and a manageable safety pro a previous biomarker-driven phase 1/2 study in iCCA patients,8 and has received U.S. and EU orphan drug designation for iCCA. Basilea is currently conducting three clinical studies with derazantinib. The first study, FIDES-01, is a phase 2 study in patients with inoperable or advanced iCCA. It comprises one cohort of patients with FGFR2 gene fusions and another cohort of patients with mutations or amplifications.9 The second study, FIDES-02, is a phase 1/2 study evaluating derazantinib alone and in combination with Roche's PD-L1 checkpoint inhibitor, atezolizumab, in patients with advanced urothelial cancer, including metastatic, or recurrent surgically unresectable disease, expressing FGFR genetic aberrations.10 The third study, FIDES-03, is a phase 1/2 study evaluating derazantinib alone and in combination with Lilly’s anti-VEGFR2 antibody ramucirumab and paclitaxel, or with Roche’s PD-L1 checkpoint inhibitor atezolizumab, in patients with advanced gastric cancer with FGFR genetic aberrations.11 Basilea has in-licensed derazantinib from ArQule Inc., a wholly-owned subsidiary of Merck & Co., Inc., Kenilworth, N.J., U.S.A. About lisavanbulin Basilea's oncology drug candidate lisavanbulin (BAL101553, the prodrug of BAL27862)12 is currently being developed as a potential therapy for glioblastoma.13, 14, 15 In preclinical studies, lisavanbulin demonstrated in-vitro and in-vivo activity against diverse treatment-resistant cancer models, including tumors refractory to conventional approved therapeutics and radiotherapy.16, 17, 18 Lisavanbulin efficiently distributes to the brain, with anticancer activity in glioblastoma models.19, 20 In preclinical studies, end-binding protein 1 (EB1) was identified as a potential response-predictive biomarker in glioblastoma models and strong EB1-positivity was shown in about 5% of tissue samples from glioblastoma patients.21, 22 The strongest expression of EB1 in non-glioblastoma tumors was detected in tissue samples from medulloblastomas and neuroblastomas, which are cancers that occur predominantly in the pediatric population. EB1-positive staining was also found in tissue samples from metastatic melanoma (skin cancer). Other tumors expressing slightly lower levels of EB1 staining include non-small cell lung cancer, colorectal cancer and triple-negative breast cancer.22 The active moiety BAL27862 binds to the colchicine site of tubulin, with distinct effects on microtubule organization,23 resulting in the activation of the "spindle assembly checkpoint" which promotes tumor cell death.24 About Basilea Basilea is a commercial-stage biopharmaceutical company founded in 2000 and headquartered in Switzerland. We are committed to discovering, developing and commercializing innovative drugs to meet the needs of patients with cancer and infectious diseases. We have successfully launched two hospital brands, Cresemba for the treatment of invasive fungal infections and Zevtera for the treatment of severe bacterial infections. We are conducting clinical studies with two targeted drug candidates for the treatment of a range of cancers and have a number of preclinical assets in both cancer and infectious diseases in our portfolio. Basilea is listed on the SIX Swiss Exchange (SIX: BSLN). Please visit basilea.com. Disclaimer This communication expressly or implicitly contains certain forward-looking statements, such as "believe", "assume", "expect", "forecast", "project", "may", "could", "might", "will" or similar expressions concerning Basilea Pharmaceutica Ltd. and its business, including with respect to the progress, timing and completion of research, development and clinical studies for product candidates. Such statements involve certain known and unknown risks, uncertainties and other factors, which could cause the actual results, financial condition, performance or achievements of Basilea Pharmaceutica Ltd. to be materially different from any future results, performance or achievements expressed or implied by such forward-looking statements. Basilea Pharmaceutica Ltd. is providing this communication as of this date and does not undertake to update any forward-looking statements contained herein as a result of new information, future events or otherwise. Derazantinib and lisavanbulin and their uses are investigational and have not been approved by a regulatory authority for any use. Efficacy and safety have not been established. The information presented should not be construed as a recommendation for use. The relevance of findings in nonclinical/preclinical studies to humans is currently being evaluated. For further information, please contact: Peer Nils Schröder, PhD Head of Corporate Communications & Investor Relations Phone +41 61 606 1102 E-mail media_relations@basilea.com investor_relations@basilea.com This press release can be downloaded from . References T. G. Hall, Y. Yu, S. Eathiraj et al. Preclinical activity of ARQ 087, a novel inhibitor targeting FGFR dysregulation. PLoS ONE 2016, 11 (9), e0162594 R. Porta, R. Borea, A. Coelho et al. FGFR a promising druggable target in cancer: Molecular biology and new drugs. Critical Reviews in Oncology/Hematology 2017 (113), 256-267 T. Helsten, S. Elkin, E. Arthur et al. The FGFR landscape in cancer: Analysis of 4,853 tumors by next-generation sequencing. Clinical Cancer Research 2016 (22), 259-267 P. McSheehy, F. Bachmann, N. Forster-Gross et al. Derazantinib (DZB): A dual FGFR/CSF1R-inhibitor active in PDX-models of urothelial cancer. Molecular Cancer Therapeutics 2019 (18), 12 supplement, pp. LB-C12 M. A. Cannarile, M. Weisser, W. Jacob et al. Colony-stimulating factor 1 receptor (CSF1R) inhibitors in cancer therapy. Journal for ImmunoTherapy of Cancer 2017, 5:53 Y. Zhu, B. L. Knolhoff, M. A. Meyer et al. CSF1/CSF1R Blockade reprograms tumor-infiltrating macrophages and improves response to T cell checkpoint immunotherapy in pancreatic cancer models. Cancer Research 2014 (74), 5057-5069 E. Peranzoni, J. Lemoine, L. Vimeux et al. Macrophages impede CD8 T cells from reaching tumor cells and limit the efficacy of anti–PD-1 treatment. Proceedings of the National Academy of Science of the United States of America 2018 (115), E4041-E4050 V. Mazzaferro, B. F. El-Rayes, M. Droz dit Busset et al. Derazantinib (ARQ 087) in advanced or inoperable FGFR2 gene fusion-positive intrahepatic cholangiocarcinoma. British Journal of Cancer 2019 (120), 165-171. ClinicalTrials.gov identifier: NCT01752920 FIDES-01: ClinicalTrials.gov identifier: NCT03230318 FIDES-02: ClinicalTrials.gov identifier: NCT04045613 FIDES-03: ClinicalTrials.gov identifier: NCT04604132 J. Pohlmann, F. Bachmann, A. Schmitt-Hoffmann et al. BAL101553: An optimized prodrug of the microtubule destabilizer B. M. Alexander, T. F. Cloughesy. Adult Glioblastoma. Journal of Clinical Oncology 2017 (35), 2402-2409 ClinicalTrials.gov identifier: NCT02490800; C. Tiu, S. Derby, N. Md. Haris et al. The potential utility of end-binding protein 1 (EB1) as response-predictive biomarker for lisavanbulin: A phase 2 study of lisavanbulin (BAL101553) in adult patients with recurrent glioblastoma. Journal of Clinical Oncology 2021, 39 (15 supplement, TPS2068) ClinicalTrials.gov identifier: NCT03250299 ClinicalTrials.gov identifier: NCT02895360 A. Sharmq, A. Broggini-Tenzer, V. Vuong et al. The novel microtubule targeting agent BAL101553 in combination with radiotherapy in treatment-refractory tumor models. Radiotherapy Oncology 2017 (124), 433-438 G. E. Duran, H. Lane, F. Bachmann et al. In vitro activity of the novel tubulin active agent BAL27862 in MDR1(+) and MDR1(-) human breast and ovarian cancer variants selected for resistance to taxanes. Cancer Research 2010, 70 (8 supplement), abstract 4412 F. Bachmann, K. Burger, G. E. Duran et al. BAL101553 (prodrug of BAL27862): A unique microtubule destabilizer active against drug refractory breast cancers alone and in combination with trastuzumab. Cancer Research 2014, 74 (19 supplement), abstract 831 A. Schmitt-Hoffmann, D. Klauer, K. Gebhardt et al. BAL27862: a unique microtubule-targeted agent with a potential for the treatment of human brain tumors. Molecular Cancer Therapeutics 2009, 8 (12 supplement), C233 A. C. Mladek, J. L. Pokorny, H. Lane et al. The novel tubulin-binding 'tumor checkpoint controller' BAL101553 has anti-cancer activity alone and in combination treatments across a panel of GBM patient-derived xenografts. Cancer Research 2016, 76 (14 supplement), abstract 4781 R. Bergès, A. Tchoghandjian, S. Honoré et al. The novel tubulin-binding checkpoint activator BAL101553 inhibits EB1-dependent migration and invasion and promotes differentiation of glioblastoma stem-like cells. Molecular Cancer Therapeutics 2016 (15), 2740-2749 M. Skowronska, C. Tiu, A. Tzankov et al. Expression of end-binding protein 1 (EB1), a potential response-predictive biomarker for lisavanbulin, in glioblastoma and various other solid tumor types. Journal of Clinical Oncology 2021, 39 (15 supplement, 3118) A. E. Prota, F. Danel, F. Bachmann et al. The novel microtubule-destabilizing drug BAL27862 binds to the colchicine site of tubulin with distinct effects on microtubule organization. Journal of Molecular Biology 2014 (426), 1848-1860 F. Bachmann, K. Burger, H. Lane. BAL101553 (prodrug of BAL27862): the spindle assembly checkpoint is required for anticancer activity. Cancer Research 2015, 75 (15 supplement), abstract 3789 Attachment Press release (PDF)

Ad hoc announcement pursuant to Art. 53 LR Basel, Switzerland, August 17, 2021 Basilea Pharmaceutica Ltd. (SIX: BSLN) announced today its financial results for the first six months ended June 30, 2021. David Veitch, Chief Executive Officer, said: “The first half of 2021 reflected a strong operational performance as we significantly increased the cash flow from our two marketed brands. In addition, we are building the basis for future growth by making good progress in our oncology development programs. Particularly encouraging are the updated efficacy data for patients with FGFR2 fusion-positive iCCA, a form of bile duct cancer, who received derazantinib within our FIDES-01 study and the continued long-lasting clinical benefit reported for EB1-positive glioblastoma patients from the phase 1/2 study with lisavanbulin.” Adesh Kaul, Chief Financial Officer, added: “As announced last year, we will have largely completed the significant change in our revenue mix in 2021. The non cash-relevant recognition of deferred revenue from upfront, development and regulatory milestone payments received in prior years, has reduced 95% year-on-year, now representing less than 3% of our total Cresemba and Zevtera related revenue. This allows a much clearer view on the significant cash contribution of our commercial business. We have reported CHF 46.1 million in total Cresemba and Zevtera non-deferred revenue, a 26% growth year-on-year. Royalty income, which most closely reflects the underlying strength of our key brand Cresemba in the major territories, grew by 27% year-on-year to CHF 23.6 million.” He continued: “We also continue to manage our cost base. We were able to keep our total cost and operating expenses at a stable level in spite of the growth of our commercial business and the continued progress in our drug development portfolio. The strong underlying operational performance is positively reflected in our operating result, which improved 40% year-on-year, when excluding the one-off profit from the sale of our headquarters property in the first half-year 2020 and the deferred revenue recognition in both periods.” Financial summary Total revenue in the first half-year 2021 was CHF 54.2 million (H1 2020: CHF 69.3 million), reflecting the already anticipated decrease in the recognition of deferred revenue to CHF 1.3 million (H1 2020: CHF 25.5 million) related to upfront, development and regulatory milestone payments received in prior years from partners. Non-deferred revenue contribution from the two marketed brands Cresemba and Zevtera increased by 26.3% to CHF 46.1 million (H1 2020: CHF 36.5 million). Other revenue amounted to CHF 6.6 million (H1 2020: CHF 7.1 million). This included CHF 5.5 million BARDA reimbursements (H1 2020: CHF 6.6 million), which are offsetting a substantial portion of the ceftobiprole phase 3 development expenses.1 The BARDA reimbursements year-on-year decreased in line with the reduced development expenses following the successful completion of the ceftobiprole phase 3 skin infection study. In the first half of 2021, investments in the pipeline resulted in research and development expenses of CHF 41.7 million (H1 2020: CHF 43.9 million). Such expenses were mainly driven by costs for the phase 3 program for ceftobiprole, the costs related to the ongoing preclinical and clinical programs for derazantinib and lisavanbulin, as well as to the ongoing pediatric programs for ceftobiprole and isavuconazole. Selling, general and administrative expenses amounted to CHF 14.4 million (H1 2020: CHF 14.5 million). In line with increasing sales of products to partners, cost of products sold increased to CHF 13.5 million (H1 2020: CHF 13.1 million). In the first half-year of 2021, the operating loss amounted to CHF 15.4 million (H1 2020: operating profit of CHF 12.8 million). The operating result H1 2020 was positively impacted by CHF 15.0 million in an one-off profit from the sale of Basilea’s headquarters property and CHF 24.2 million higher deferred revenue related to upfront and milestone payments from Astellas, Pfizer and Gosun, which were all fully recognized in FY 2020. The net loss amounted to CHF 19.9 million (H1 2020: net profit of CHF 9.9 million), resulting in a basic and diluted loss per share of CHF 1.84 (H1 2020: basic earnings and diluted earnings per share of CHF 0.92 and CHF 0.91, respectively). Net cash used in operating activities in H1 2021 was reduced by 18.1% to CHF 27.2 million as compared to CHF 33.2 million in H1 2020. This improvement is a result, on the one hand of the significant increase in cash inflow, based on the growth of Cresemba and Zevtera non-deferred revenue contributions and on the other hand, of Basilea’s continued focus on managing operating expenses, by continuously optimizing investments into the preclinical and clinical portfolio and improving the cost base through strategic transactions. Cash and investments amounted to CHF 164.7 million as of June 30, 2021, compared to CHF 167.3 million as of December 31, 2020. The convertible bond maturing in December 2022 (ISIN CH0305398148) was reduced by CHF 12.4 million in H1 2021. Key financial figures Note: Consolidated figures in conformity with U.S. GAAP; rounding was applied consistently. The unaudited, condensed consolidated interim financial statements of Basilea Pharmaceutica Ltd. for the first half-year 2021 can be found on the Company’s website at . FY 2021 financial guidance Basilea increases its revenue guidance and expects a better operating result for full-year 2021: * Excluding any impact from a reduction of the outstanding convertible bonds Corporate events: divestment of Chinese R&D subsidiary – private placement with institutional investors Divestment of Basilea Pharmaceutica China: increases flexibility in the procurement of external research and development services and helps to better adapt the cost structure to the respective project portfolio. In April 2021, Basilea announced that it has completed the divestment of its Chinese research and development subsidiary to the U.S.-based custom manufacturing organization PHT International Inc. for an initial payment of USD 2.5 million (CHF 2.3 million). In addition, Basilea is entitled to receive additional payments of USD 3.8 million (CHF 3.6 million) over the next three years. Private placement: provides further financial flexibility and opens up a number of strategic opportunities for the further development of oncology drug candidates In February 2021, Basilea carried out a strategic capital increase in the form of a private placement with institutional investors, which generated gross proceeds of around CHF 46 million. Continued reduction of 2022 convertible bond further improves debt ratio Since the beginning of the year, Basilea reduced the convertible bond maturing in December 2022 (ISIN CH0305398148) by CHF 12.4 million. Portfolio progress: three clinical studies expected to report topline results until mid-2022 – clinical pipeline expansion expected – significant progress made in commercialization of marketed brands FGFR inhibitor derazantinib1: further strengthened differentiated efficacy and safety profile Encouraging topline results have been reported for cohort 1 (FGFR2 fusion-positive iCCA) of the FIDES-01 phase 2 study in February 2021.2 These data further matured during patient follow-up and with data cut-off in April 2021 showed a median progression-free survival (PFS) of 7.8 months, which is in the upper range reported for this endpoint with FGFR inhibitors in this patient population.2 This further supports the clinically relevant efficacy for derazantinib monotherapy in this indication. For cohort 2 of FIDES-01 (iCCA with FGFR2 mutations/amplifications), positive interim results were published in March and topline results for this cohort are expected in the first half of 2022. In the FIDES-02 urothelial cancer study, interim results for the cohort with patients who failed to respond to other FGFR inhibitors are expected in the second half of 2021, both for monotherapy with derazantinib and in combination with Roche’s atezolizumab.3 In May 2021, Basilea decided to also explore higher daily doses for mono- as well as combination therapy in the FIDES-02 and FIDES-03 studies (FGFR-driven urothelial and gastric cancer, respectively).4 Initial results from cohorts receiving this intensified dose regimen are expected in the first half of 2022. Lisavanbulin: potential expansion of lisavanbulin into other tumors based on biomarker signature – orphan drug designation granted Basilea is currently investigating its tumor checkpoint controller lisavanbulin in patients with glioblastoma.5 Glioblastoma is the most common type of primary brain cancer and one of the most lethal types of cancer.6 Two patients from the phase 1 part of the ongoing clinical study, whose tumors tested positive on the potential response-predictive biomarker EB1, are showing a long-lasting clinical benefit and have been successfully treated for more than two years. One of these patients even experienced a reduction of tumor size of more than 80%. In the phase 2 part of the study, only EB1-positive glioblastoma patients are being enrolled and Basilea expects interim results at the end of 2021 and topline results in the first half of 2022. If these results provide a clinical proof-of-concept in glioblastoma, this would support exploring the selection of patients based on EB1-positivity in other tumor types as well, such as melanoma, breast, colorectal and lung cancers, or rare cancer types such as medulloblastomas or neuroblastomas. Approximately 5% of glioblastoma tissue samples were found to be EB1-positive. In July 2021, the U.S. Food and Drug Administration (FDA) granted lisavanbulin Orphan Drug Designation for the treatment of malignant glioma, which includes glioblastoma. This is positive news as the designation qualifies for various incentives, including longer regulatory market exclusivity. Pipeline expansion: new oncology drug candidate expected to enter clinical studies early 2022 Basilea is making encouraging progress in final preclinical studies with a potential first-in-class small-molecule kinase inhibitor, which was in-licensed in 2018. If successfully completed, Basilea plans to file an IND (Investigational New Drug) application later this year. If the IND is granted, first-in-human clinical studies could be initiated in early 2022. Cresemba (isavuconazole): global “in-market” sales continue to increase – progress in Japan and China Cresemba has reached USD 266 million global “in-market” sales for the 12 months to the end of March 2021.7 This is an increase of 18% year-on-year. Cresemba is currently approved in almost 60 countries and has been launched in 53 countries. Thus, Basilea is well on track to achieve the target of 60 launched countries by the end of this year and is targeting to increase this to approximately 70 countries by the end of 2022. In January 2021, the last patient was enrolled in a phase 3 study in deep-seated mycoses, conducted by Basilea’s partner Asahi Kasei Pharma.8 At the end of July, Asahi Kasei Pharma announced that the study was successfully completed and that they are planning to file a New Drug Application (NDA) for the marketing authorization of Cresemba in Japan. In China, the review of the marketing authorization applications which were accepted for review in May and October 2020 (for mucormycosis and for invasive aspergillosis respectively), is ongoing. Zevtera (ceftobiprole): expanding commercial partnerships and making progress in key study for potential U.S. approval In July, Basilea announced another distribution agreement, with Moscow-based JSC Lancet for Russia and the other countries of the Eurasian Economic Union. In order to gain market access to the commercially most important U.S. market, Basilea is conducting a phase 3 program of two cross-supportive studies.9 The program was agreed with the FDA in a Special Protocol Assessment. The first of the two studies, the TARGET study that explored ceftobiprole for the treatment of complicated skin infections, was successfully completed in 2019.10 The second study, the ERADICATE study in Staphylococcus aureus bacteremia (SAB), is on track to complete patient enrolment around the end of 2021, with topline results in the first half of 2022.11 Innovative anti-infectives: received CARB-X grant for development of novel antibiotic In May, Basilea was awarded an up to USD 2.7 million research grant from CARB-X (Combating Antibiotic-Resistant Bacteria Biopharmaceutical Accelerator), a global partnership dedicated to supporting the early development of antibacterial products, for the development of DXR inhibitors, a novel class of antibiotics targeting drug-resistant Gram-negative bacteria such as carbapenem-resistant Enterobacterales, Acinetobacter baumannii and multidrug-resistant Pseudomonas aeruginosa. Conference call and webcast Basilea Pharmaceutica Ltd. will host a conference call and webcast today, Tuesday, August 17, 2021, at 4 p.m. (CEST), to discuss the Company’s financial and operating results. Via audio webcast with presentation The live audio webcast of the results presentation can be followed here. Please note that there is no function to ask questions via webcast. For questions, please additionally dial-in via phone (see below). Via phone To listen by phone and ask questions, please use the dial-in details below. To ensure prompt access, please call approximately five minutes prior to the scheduled start of the call. Replay The webcast, along with presentation will be available online shortly after the event and accessible for three months. About Basilea Basilea is a commercial-stage biopharmaceutical company founded in 2000 and headquartered in Switzerland. We are committed to discovering, developing and commercializing innovative drugs to meet the medical needs of patients with cancer and infectious diseases. We have successfully launched two hospital brands, Cresemba for the treatment of invasive fungal infections and Zevtera for the treatment of severe bacterial infections. We are conducting clinical studies with two targeted drug candidates for the treatment of a range of cancers and have a number of preclinical assets in both cancer and infectious diseases in our portfolio. Basilea is listed on the SIX Swiss Exchange (SIX: BSLN). Please visit basilea.com. Disclaimer This communication expressly or implicitly contains certain forward-looking statements, such as "believe", "assume", "expect", "forecast", "project", "may", "could", "might", "will" or similar expressions concerning Basilea Pharmaceutica Ltd. and its business, including with respect to the progress, timing and completion of research, development and clinical studies for product candidates. Such statements involve certain known and unknown risks, uncertainties and other factors, which could cause the actual results, financial condition, performance or achievements of Basilea Pharmaceutica Ltd. to be materially different from any future results, performance or achievements expressed or implied by such forward-looking statements. Basilea Pharmaceutica Ltd. is providing this communication as of this date and does not undertake to update any forward-looking statements contained herein as a result of new information, future events or otherwise. Derazantinib and lisavanbulin and their uses are investigational and have not been approved by a regulatory authority for any use. Efficacy and safety have not been established. The information presented should not be construed as a recommendation for use. The relevance of findings in nonclinical/preclinical studies to humans is currently being evaluated. For further information, please contact: This ad hoc announcement can be downloaded from . References Attachment

Basel, Switzerland, June 07, 2021 Basilea Pharmaceutica Ltd. (SIX: BSLN) announced today that data on the prevalence of end-binding protein 1 (EB1) in glioblastoma and other tumor types is being presented at the American Society of Clinical Oncology (ASCO) Annual Meeting that takes place online from June 4 to 8, 2021. EB1 plays a pivotal role in the regulation of microtubule dynamics during cell division and has been shown to interact with microtubule-targeting agents, such as lisavanbulin, inhibiting tumor growth.1 EB1 has been identified as a response-predictive biomarker for Basilea’s tumor checkpoint controller lisavanbulin in pre-clinical glioblastoma models.2 In the previously reported phase 1 portion of the ongoing phase 1/2 clinical study, long-lasting clinical benefit was observed in two patients with recurrent glioblastoma whose tumor tissues show EB1-positive staining. Both patients are ongoing in the study for more than 2 years.3 The prevalence assessment of EB1-positivity or strong EB1-staining using immunohistochemistry methods presented at ASCO was based on 565 patient tissue samples from 14 different tumor types, including more than 100 glioblastoma samples. Approximately 5% of glioblastoma tissue samples were found to be EB1-positive. The strongest expression of EB1 in non-glioblastoma tumors was detected in tissue samples from medulloblastomas and neuroblastomas, which are cancers that occur predominantly in the pediatric population. EB1-positive staining was also found in tissue samples from metastatic melanoma (skin cancer). Other tumors expressing slightly lower levels of EB1 staining include non-small cell lung cancer, colorectal cancer and triple-negative breast cancer.4 Dr. Marc Engelhardt, Chief Medical Officer, commented: ”We are very pleased that two patients with EB1-positive recurrent glioblastoma have obtained long-lasting clinical benefit in our phase 1 study with lisavanbulin. We are looking forward to the interim results in our phase 2 study, which is enrolling patients with recurrent glioblastoma that is EB1-positive, towards the end of 2021. The new prevalence data presented at ASCO are consistent with our initial frequency estimates of EB1-positive glioblastoma. A clinical proof-of-concept in glioblastoma based on positive interim results would support exploring the selection of patients based on EB1-positivity in other tumor types as well, such as melanoma, breast, colorectal and lung cancers or rare cancer types such as medulloblastomas or neuroblastomas.” The rationale and study design of the ongoing phase 2 study with lisavanbulin in patients with EB1-positive recurrent glioblastoma is being presented in a second poster at the ASCO Annual meeting.5 For further information, please visit About lisavanbulin (BAL101553) Basilea's oncology drug candidate lisavanbulin (BAL101553, the prodrug of BAL27862)6 is being developed as a potential therapy for diverse cancers.1, 7, 8 In preclinical studies, lisavanbulin demonstrated in-vitro and in-vivo activity against diverse treatment-resistant cancer models, including tumors refractory to conventional approved therapeutics and radiotherapy.9, 10, 11Lisavanbulin efficiently distributes to the brain, with anticancer activity in glioblastoma models.12, 13 In preclinical studies, end-binding protein 1 (EB1) was identified as a potential response-predictive biomarker in glioblastoma models.2 The active moiety BAL27862 binds to the colchicine site of tubulin, with distinct effects on microtubule organization,14 resulting in the activation of the "spindle assembly checkpoint" which promotes tumor cell death.15 About Basilea Basilea is a commercial-stage biopharmaceutical company founded in 2000 and headquartered in Switzerland. We are committed to discovering, developing and commercializing innovative drugs to meet the medical needs of patients with cancer and infectious diseases. We have successfully launched two hospital brands, Cresemba for the treatment of invasive fungal infections and Zevtera for the treatment of severe bacterial infections. We are conducting clinical studies with two targeted drug candidates for the treatment of a range of cancers and have a number of preclinical assets in both cancer and infectious diseases in our portfolio. Basilea is listed on the SIX Swiss Exchange (SIX: BSLN). Please visit basilea.com. Disclaimer This communication expressly or implicitly contains certain forward-looking statements, such as "believe", "assume", "expect", "forecast", "project", "may", "could", "might", "will" or similar expressions concerning Basilea Pharmaceutica Ltd. and its business, including with respect to the progress, timing and completion of research, development and clinical studies for product candidates. Such statements involve certain known and unknown risks, uncertainties and other factors, which could cause the actual results, financial condition, performance or achievements of Basilea Pharmaceutica Ltd. to be materially different from any future results, performance or achievements expressed or implied by such forward-looking statements. Basilea Pharmaceutica Ltd. is providing this communication as of this date and does not undertake to update any forward-looking statements contained herein as a result of new information, future events or otherwise. For further information, please contact: This press release can be downloaded from . References Attachment