ADC Therapeutics Announces Interim Phase I Data from its Novel Antibody-Drug Conjugate ADCT-301

ADC Therapeutics (ADCT), an oncology drug discovery and development company that specializes in the development of proprietary Antibody Drug Conjugates (ADCs) targeting major cancers, today announced clinical data from two ongoing Phase I clinical trials evaluating ADCT-301 (camidanlumab tesirine or “Cami-T”) in important subtypes of lymphoma and leukemia. The data were presented at the 59^th American Society of Hematology (ASH) Annual Meeting in Atlanta, USA.

1. Interim results of a Phase I open label, single agent, dose-escalating study of ADCT-301 evaluating tolerability, safety, pharmacokinetics and efficacy in patients with relapsed or refractory B-cell Hodgkin’s or non-Hodgkin’s lymphoma

Dr. Steven M. Horwitz, Medical Oncologist at Memorial Sloan Kettering Cancer Center in New York City, and Principal Investigator, said: “Despite considerable advances in the treatment of lymphoma, a significant number of patients still relapse or become refractory to existing therapies and need new treatment options. We are excited by the 77 percent overall response rate (ORR) in Hodgkin Lymphoma (HL), including a 44 percent complete response rate. We are also seeing emerging efficacy signals in T-cell lymphomas (ORR: 33 percent) and B-cell lymphomas (ORR: 19 percent). Although still early, we are very encouraged by a median duration of response for HL patients of over 5 months to-date. The safety profile appears consistent with what we expect with this target and warhead. We are now working to determine the best dosing regimen for Phase II.“

Data were presented from 86 evaluable, heavily pre-treated patients who had failed, or were intolerant to, any established therapy known to provide clinical benefit. The median age of patients was 53 years and they had a median of 4 prior therapies. Data were reported from Part 1 and Part 2 of the Phase I study as of November 1, 2017. In Part 1 (dose escalation), 71 patients were treated at dose ranges from 3-150 µg/kg every three weeks. In Part 2 (dose expansion), 15 Hodgkin Lymphoma patients were treated at 45 µg/kg every 3 weeks.

Key findings presented at the poster presentation included:

• For the 27 response-evaluable patients with HL in Part 1, treated at doses greater than or equal to 45 µg/kg, the ORR was 77 percent (21/27 patients) with 12 patients achieving a complete response (44 percent) and 9 patients achieving a partial response (33 percent).
• For the 12 response-evaluable patients with HL in Part 1 and Part 2, treated at the 45 µg/kg dose, the ORR was 100 percent (12/12) with 6 patients achieving a complete response (50 percent) and 6 patients achieving a partial response (50 percent).
• For HL patients in Part 1 and Part 2, treated at doses greater than or equal to 45 µg/kg, a complete or partial response was achieved in 21 of 27 patients previously treated with brentuximab vedotin (77 percent), 13 of 18 patients previously treated with a checkpoint inhibitor (72 percent), 9 of 14 patients who had previously undergone a stem cell transplantation (64 percent), and 4 of 8 patients who had previously received all three of these treatments (50 percent).
• ADCT-301 has been reasonably well tolerated.
• The most common treatment-emergent adverse events of any grade occurring in at least 20 percent of patients in Part 1 and Part 2 were fatigue (30 percent), rash (26 percent), elevated gamma-glutamyltransferase (22 percent), and pyrexia (21 percent). The most common Grade 3 or 4 adverse events occurring in at least 5 percent of patients, regardless of attribution, were elevated gamma-glutamyltransferase (13 percent), reduced platelet count (9 percent), elevated alanine aminotransferase (6 percent), anemia (6 percent), and rash (6 percent). There were three heavily pre-treated patients diagnosed with auto-immune neurotoxicity, including two patients who developed Guillain-Barré syndrome.
• These encouraging preliminary safety and efficacy results support further characterization of the dosing regime to optimize the therapeutic window in Hodgkin Lymphoma for a Phase II study.

2. Interim results of a Phase I open label, single agent, dose-escalating study of ADCT-301 evaluating tolerability, safety, pharmacokinetics and efficacy in patients with relapsed or refractory B-cell acute myeloid leukemia or acute lymphoblastic leukemia

Data were presented from 33 evaluable, heavily pre-treated, patients who had failed, or were intolerant to, any established therapy known to provide clinical benefit. The median age of patients was 67 years and they had a median of 3 prior therapies. In Part 1 (dose escalation), 33 patients were treated at dose ranges from 3-92 µg/kg every three weeks, or 30-37.5 µg/kg once weekly.

Key findings presented at the poster presentation included:

• One patient achieved a complete response with incomplete blood count recovery.
• ADCT-301 has shown an acceptable safety profile.
• The most common treatment-emergent adverse events of any grade occurring in at least 20 percent of patients were fatigue (30 percent), nausea (24 percent), febrile neutropenia (21 percent), and pneumonia (21 percent). The most common Grade 3 or 4 adverse events occurring in at least 10 percent of patients, regardless of attribution, were febrile neutropenia (21 percent), thrombocytopenia (15 percent), fatigue (12 percent), reduced neutrophil count (12 percent), and pneumonia (12 percent).
• Dose escalation will continue to investigate weekly dosing.

About ADCT-301

ADCT-301 is an antibody-drug conjugate (ADC) composed of a monoclonal antibody that binds to CD25 (HuMax®-TAC, licensed from Genmab A/S), conjugated to a pyrrolobenzodiazepine (PBD) dimer toxin. Once bound to a CD25-expresing cell, ADCT-301 is internalized into the cell where enzymes release the PBD-based warhead. CD25 is an attractive target for an ADC approach as it is expressed in a wide range of hematological malignancies, including certain forms of lymphomas and leukemias, while its expression in healthy organs is restricted. ADCT-301 is being evaluated in two ongoing phase Ia/Ib clinical trials in patients with relapsed or refractory Hodgkin lymphoma (HL) and non-Hodgkin lymphoma (NHL), and in patients with relapsed or refractory CD25-positive acute myeloid leukemia (AML) and acute lymphoblastic leukemia (ALL). (www.adct-301.com)

About ADC Therapeutics

ADC Therapeutics SA (ADCT) is an oncology drug development company that specializes in the development of proprietary antibody drug conjugates (ADCs) targeting major types of hematological malignancies and solid tumors. The Company’s ADCs are highly targeted biopharmaceutical drugs that combine monoclonal antibodies specific to surface antigens present on particular tumor cells with a novel class of highly potent pyrrolobenzodiazepine (PBD) based warheads via a chemical linker. The Company has four PBD-based antibody drug conjugates in six ongoing Phase Ia and Ib clinical trials in the USA and in Europe, and a deep pipeline of other preclinical ADCs in development. ADCT enjoys strong relationships with world class partners, including AstraZeneca and its global biologics research and development arm, MedImmune. The Company is based in Lausanne (Biopôle), Switzerland and has operations in London, San Francisco and New Jersey. (www.adctherapeutics.com).

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Contact information

ADC Therapeutics
Dr. Chris Martin, +41 (0) 21 653 0200
Chief Executive Officer
chris.martin@adctherapeutics.com
or
Dynamics Group
Alexandre Müller, +41 (0) 43 268 3231
amu@dynamicsgroup.ch