CTPS1

Step Pharma to Present Promising Data on the Therapeutic Potential of Selective Small Molecule Inhibition of CTPS1 at the 64th American Society of Hematology Annual Meeting St. Genis-Pouilly, France, 3 November - Step Pharma, the world leader in CTPS1 inhibition for the targeted treatment of cancer, today announces that it will be presenting pre-clinical data on its lead candidate STP938 at the 64th American Society of Hematology Annual Meeting being held from the 10-13 December, 2022 in New Orleans, Louisiana and virtually. Step Pharma and collaborators will present two posters on STP938, its potent and highly selective small molecule inhibitor of CTPS1, reporting its potential as a targeted therapeutic for the treatment of Mantle Cell Lymphoma and Multiple Myeloma. Full details of the posters are: Poster presentation: CTPS1 is a Novel Therapeutic Target in Multiple Myeloma that Synergizes with Inhibition of ATR, CHEK1 or WEE1 Authors: Christina Pfeiffer, Alexander Grandits, Hélène Asnagli, Anja Schneller, Julia Huber, Niklas Zojer, Martin Schreder, Andrew Parker, Arnold Bolomsky*, Philip Beer*, Heinz Ludwig* * co-senior authors Date and Time: Available online from November 3, 09:00 EDT on the Congress platform Poster Presentation: STP938, a Selective CTPS1 Inhibitor, Shows Single Agent Activity and Synergy with BCL2 Inhibition in Preclinical Models of Mantle Cell Lymphoma Authors: David Chiron, PhD, Emmanuelle Menoret, PhD, Charlotte Kervoelen, PhD, Sophie Maïga, Celine Bellanger, Benoit Tessoulin, MD, Cyrille Touzeau, Hélène Asnagli, PhD, Andy Parker, PhD, Philip Beer, MD, PhD and Catherine Pellat-Deceunynck, PhD Date and Time: Available online from November 3, 09:00 EDT on the Congress platform -Ends- About Step PharmaStep Pharma’s goal is to bring about a step change in how cancer is treated with targeted therapies that kill cancer cells and leave healthy cells unharmed. The Company is the world leader in CTPS1 inhibition, a new approach with the potential to yield highly selective, safe and effective cancer treatments for both blood cancers and solid tumours. The Company’s lead product STP938 has received both IND and CTA clearance to proceed into first in human trials in the US and UK for the treatment of T cell and B cell lymphomas. Clinical trials in lymphoma commenced in September 2022. STP938 has the potential to be the backbone of a multitude of cancer therapies as well as a potent monotherapy for hard-to-treat blood cancers. Step Pharma was founded in 2014 by Kurma Partners, the Imagine Institute and Sygnature Discovery, based on the scientific discoveries of Prof. Alain Fischer and Dr Sylvain Latour. Step Pharma is based in Saint-Genis-Pouilly, France, and is supported by a strong syndicate of investors led by Kurma Partners and including Bpifrance (Fonds Biothérapies Innovantes et Maladies Rares and InnoBio2 Fund), Pontifax, Hadean Ventures, Sunstone Life Science Ventures, Inserm Transfert Initiative, Idinvest, Sygnature Discovery and the Imagine Institute. More information on the company can be found at www.step-ph.com. For more information please contact: Step PharmaAndrew Parker, Chief Executive Officercontact@step-ph.com Consilium Strategic CommunicationsAmber Fennell, Namrata Taak, Stella LempidakiTel: +44 (0) 20 3709 5700steppharma@consilium-comms.com

PRESS RELEASE Step Pharma Announces First Patient Dosed with STP938, the World’s Most Advanced CTPS1 Inhibitor, in a Phase 1/2 Trial for T cell and B cell lymphomas Potential first-in-class targeted treatment for relapsed/refractory T cell and B cell lymphomas St. Genis-Pouilly, France, 24 October 2022 - Step Pharma, the world leader in CTPS1 inhibition for the targeted treatment of cancer, announces today that the first patient has been successfully dosed with STP938, in a Phase 1/2 trial in adult subjects with relapsed/refractory B cell and T cell lymphomas. The dose-escalation part of the open label, non-randomised Phase 1/2 trial comprises multiple cohorts dosed with STP938, administered as an oral monotherapy, ascending in a stepwise manner. The primary objective in Phase I is to assess the safety and tolerability of STP938. Brian Schwartz, Chief Medical Officer of Step Pharma, commented: “We are developing STP938, a highly selective, first-in-class treatment based on ground-breaking genetics. The dosing of the first patient into our Phase 1/2 trial is an important step to identify an optimal dose to take forward into further clinical development for relapsed/ refractory T cell and B cell lymphomas.” STP938 is a first-in-class oral cancer therapeutic that specifically inhibits nucleotide synthesis and the enzyme cytidine triphosphate synthase 1 (CTPS1) in particular, originally identified as an essential gene for lymphocyte proliferation. By targeting CTPS1, Step Pharma has unlocked the ability to selectively target the de novo pyrimidine synthesis pathway in cancer cells. This ground-breaking approach should enable the highly selective treatment of both blood cancers and solid tumours. Further details of the study can be found on clinicaltrials.gov under the identifier NCT05463263. -Ends- About Step PharmaStep Pharma’s goal is to bring about a step change in how cancer is treated with targeted therapies that kill cancer cells and leave healthy cells unharmed. The Company is the world leader in CTPS1 inhibition, a new approach with the potential to yield highly selective, safe and effective cancer treatments for both blood cancers and solid tumours. The Company’s lead product STP938 has received both IND and CTA clearance to proceed into first in human trials in the US and UK for the treatment of T cell and B cell lymphomas. Clinical trials in lymphoma commenced in September 2022. STP938 has the potential to be the backbone of a multitude of cancer therapies as well as a potent monotherapy for hard-to-treat blood cancers. Step Pharma was founded in 2014 by Kurma Partners, the Imagine Institute and Sygnature Discovery, based on the scientific discoveries of Prof. Alain Fischer and Dr Sylvain Latour. Step Pharma is based in Saint-Genis-Pouilly, France, and is supported by a strong syndicate of investors led by Kurma Partners and including Bpifrance (Fonds Biothérapies Innovantes et Maladies Rares and InnoBio2 Fund), Pontifax, Hadean Ventures, Sunstone Life Science Ventures, Inserm Transfert Initiative, Idinvest, Sygnature Discovery and the Imagine Institute. More information on the company can be found at www.step-ph.com. For more information please contact: Step PharmaAndrew Parker, Chief Executive Officercontact@step-ph.com Consilium Strategic CommunicationsAmber Fennell, Namrata Taak, Stella LempidakiTel: +44 (0) 20 3709 5700steppharma@consilium-comms.com

St. Genis-Pouilly, France, 28 July 2022 - Step Pharma, a world leader in CTPS1 inhibition for the targeted treatment of cancer, announces today that its lead asset STP938 has cleared both an Investigational New Drug (IND) application by the Food and Drug Administration (FDA), and a clinical trial application (CTA) by the UK’s Medicines and Healthcare products Regulatory Agency (MHRA), enabling Step Pharma to progress STP938, its first-in-class, selective CTPS1 inhibitor into the clinic in the US and UK. STP938 has now entered an open label, first-in-human, Phase 1/2 study to evaluate the safety, tolerability, pharmacokinetics, and preliminary efficacy of STP938 in adult subjects with relapsed/refractory B cell and T cell lymphomas. Further details of the study can be found on clinicaltrials.gov under the identifier NCT05463263. Patients with such cancers currently face high relapse rates from existing treatments. Step Pharma is pioneering a novel class of oral drugs that specifically inhibits nucleotide synthesis and the enzyme cytidine triphosphate synthase 1 (CTPS1) in particular, originally identified as an essential gene for lymphocyte proliferation. By targeting CTPS1, Step Pharma has unlocked the ability to selectively target the de novo pyrimidine synthesis pathway in cancer cells. This ground-breaking approach should enable the highly selective treatment of both blood cancers and solid tumours. Andrew Parker, Chief Executive Officer of Step Pharma, said: “Our unique approach to cancer treatment has the potential to yield a novel targeted cancer therapy that can form the backbone of both blood and solid tumour cancer treatment regimens. We are delighted to have moved STP938 into the clinic for hard-to-treat lymphomas with the ultimate goal of improving the lives of millions of cancer patients.” Brian Schwartz, Chief Medical Officer of Step Pharma, commented: “The clinical trial approvals by both the US FDA and UK MHRA are a significant milestone for Step Pharma and our highly differentiated lead candidate STP938, as we become a clinical-stage company and move at speed to bring this first-in-class treatment to cancer patients with high unmet medical needs.” Step Pharma will initially investigate STP938 in blood cancers, with a focus on T cell lymphomas, where there has been no improvement in five-year survival rates for over 20 years. However, as studies have shown that all cancer cells require CTPS1 for DNA synthesis, STP938 could be a key component of a multitude of cancer treatment regimens. -Ends- About Step Pharma Step Pharma’s goal is to bring about a step change in how cancer is treated with targeted therapies that kill cancer cells and leave healthy cells unharmed. The Company is the world leader in CTPS1 inhibition, a new approach with the potential to yield highly selective, safe and effective cancer treatments for both blood cancers and solid tumours. The Company’s lead product STP938 has received both IND and CTA clearance to proceed into first in human trials in the US and UK for the treatment of T cell and B cell lymphomas. Clinical trials in lymphoma commenced in the second half of 2022. STP938 has the potential to be the backbone of a multitude of cancer therapies as well as a potent monotherapy for hard-to-treat blood cancers. Step Pharma was founded in 2014 by Kurma Partners, the Imagine Institute and Sygnature Discovery, based on the scientific discoveries of Prof. Alain Fischer and Dr Sylvain Latour. Step Pharma is based in Saint-Genis-Pouilly, France, and is supported by a strong syndicate of investors led by Kurma Partners and including Bpifrance (Fonds Biothérapies Innovantes et Maladies Rares and InnoBio2 Fund), Pontifax, Hadean Ventures, Sunstone Life Science Ventures, Inserm Transfert Initiative, Idinvest, Sygnature Discovery and the Imagine Institute. More information on the company can be found at www.step-ph.com.