Company Announcements

Oral presentation shows ADCT-242 targeting Claudin-6 was well-tolerated and demonstrated potent
 antitumor activity in ovarian and non-small lung cancer

Poster presentations highlight antitumor activity and safety of novel PSMA-targeted and ASCT2-
targeted ADCs

LAUSANNE, Switzerland, April 28, 2025 /PRNewswire/ -- ADC Therapeutics SA (NYSE: ADCT), a commercial-stage global leader and pioneer in the field of antibody drug conjugates (ADCs), today announced data from preclinical studies of three exatecan-based antibody drug conjugates (ADCs) targeting Claudin-6 (CLDN6), prostate-specific membrane antigen (PSMA), and Alanine, Serine, Cysteine Transporter 2 (ACST2) as presented at the American Association for Cancer Research (AACR) Annual Meeting 2025.

"We believe these presentations demonstrate the strong potential of our exatecan-based ADCs to treat a wide range of solid and hematologic cancers beyond lymphoma. The data from the oral presentation of our CLDN6-targeted ADC show its potential, both as a single agent and in combination, to treat ovarian and non-small cell lung cancers," said Patrick van Berkel, PhD, Chief Scientific Officer of ADC Therapeutics. "Our additional presentations showcase compelling data validating the potency and tolerability of our PSMA-targeting and ASCT2-targeting ADCs."

Data from the preclinical investigation of ADCT-242, a novel exatecan-based ADC targeting CLDN6, were presented in an oral presentation titled, "Preclinical investigation of ADCT-242, a novel exatecan-based antibody drug conjugate targeting Claudin-6, as single agent or in combination in ovarian and non-small lung cancer models." Key highlights from this presentation include:

• ADCT-242 demonstrated potent anti-tumor activity in vivo in PA-1 and OVCAR-3 xenograft models with medium CLDN6 expression
• CLDN6-dependent anti-tumor activity of ADCT-242 was observed in lung patient-derived tumor models
• ADCT-242 was tolerated in mice or cynomolgus monkeys at doses up to 150 mg/kg or 40 mg/kg, respectively, indicative of a good therapeutic index

Data from the preclinical investigation of ADCT-241, a novel PSMA-targeting ADC, were presented in a poster presentation titled, "Preclinical Development of ADCT-241, a Novel Exatecan-based Antibody-Drug Conjugate Targeting PSMA for the Treatment of Prostate Cancer." The data demonstrated antitumor activity in both xenograft and patient-derived PSMA-expressing prostate cancer models as well as synergy with enzalutamide. ADCT-241 was well tolerated in both rats and cynomolgus monkeys.

Data from the preclinical investigation of HuB14-VA-PL2202, a novel ASCT2-targeting ADC, were presented in a poster presentation titled, "HuB14-VA-PL2202, a novel antibody-drug conjugate targeting ASCT2, a novel ADC target over-expressed in both solid and hematological cancers." The data demonstrated potent and specific in vitro and in vivo antitumor activity of HuB14-VA-PL2202 in ASCT2-positive solid and hematological cancer cell lines, and HuB14-VA-PL2202 was well-tolerated in cynomolgus monkeys.

To access the full AACR Annual Meeting 2025 program, visit the AACR Annual Meeting website.

About ADC Therapeutics

ADC Therapeutics (NYSE: ADCT) is a commercial-stage global leader and pioneer in the field of antibody drug conjugates (ADCs). The Company is advancing its proprietary ADC technology to transform the treatment paradigm for patients with hematologic malignancies and solid tumors.

ADC Therapeutics' CD19-directed ADC ZYNLONTA (loncastuximab tesirine-lpyl) received accelerated approval by the FDA and conditional approval from the European Commission for the treatment of relapsed or refractory diffuse large B-cell lymphoma after two or more lines of systemic therapy. ZYNLONTA is also in development in combination with other agents and in earlier lines of therapy. In addition to ZYNLONTA, ADC Therapeutics has multiple ADCs in ongoing clinical and preclinical development.

ADC Therapeutics is based in Lausanne (Biopôle), Switzerland and has operations in London, the San Francisco Bay Area and New Jersey. For more information, please visit https://adctherapeutics.com/ and follow the Company on LinkedIn.

ZYNLONTA^® is a registered trademark of ADC Therapeutics SA.

Forward-Looking Statements
This press release contains forward-looking statements within the meaning of the safe harbor provisions of the Private Securities Litigation Reform Act of 1995. In some cases you can identify forward-looking statements by terminology such as "may", "will", "should", "would", "expect", "intend", "plan", "anticipate", "believe", "estimate", "predict", "potential", "seem", "seek", "future", "continue", or "appear" or the negative of these terms or similar expressions, although not all forward-looking statements contain these identifying words. Forward-looking statements are subject to certain risks and uncertainties that can cause actual results to differ materially from those described. Factors that may cause such differences include, but are not limited to: the timing and future results of the Company's early research in exatecan-based Claudin-6, PSMA and ASCT2-targeting antibody-drug conjugates; the expected cash runway into mid-2026 the Company's ability to grow ZYNLONTA^® revenue in the United States; the ability of our partners to commercialize ZYNLONTA^® in foreign markets, the timing and amount of future revenue and payments to us from such partnerships and their ability to obtain regulatory approval for ZYNLONTA^® in foreign jurisdictions; the timing and results of the Company's or its partners' research and development projects or clinical trials including LOTIS 5 and 7 and ADCT 602; the timing and results of investigator-initiated trials including those studying FL and MZL and the potential regulatory and/or compendia strategy and the future opportunity; the timing and outcome of regulatory submissions for the Company's products or product candidates; actions by the FDA or foreign regulatory authorities; projected revenue and expenses; the Company's indebtedness, including Healthcare Royalty Management and Blue Owl and Oaktree facilities, and the restrictions imposed on the Company's activities by such indebtedness, the ability to comply with the terms of the various agreements and repay such indebtedness and the significant cash required to service such indebtedness; and the Company's ability to obtain financial and other resources for its research, development, clinical, and commercial activities. Additional information concerning these and other factors that may cause actual results to differ materially from those anticipated in the forward-looking statements is contained in the "Risk Factors" section of the Company's Annual Report on Form 10-K and in the Company's other periodic and current reports and filings with the U.S. Securities and Exchange Commission. These statements involve known and unknown risks, uncertainties and other factors that may cause actual results, performance, achievements or prospects to be materially different from any future results, performance, achievements or prospects expressed in or implied by such forward-looking statements. The Company cautions investors not to place undue reliance on the forward-looking statements contained in this document.

CONTACTS:

Investors
Marcy Graham
ADC Therapeutics
Marcy.Graham@adctherapeutics.com
+1 650-667-6450

Media
Nicole Riley
ADC Therapeutics
Nicole.Riley@adctherapeutics.com
+1 862-926-9040

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SOURCE ADC Therapeutics SA