The aim of the study is to assess the safety and tolerability of increasing doses of ATOR-1017 when administered as repeated intravenous infusions to patients with advanced and/or refractory solid malignancies.

Major Inclusion Criteria:

A patient is eligible to be included in the study if all the following criteria apply:

• Has a diagnosis of advanced and/or refractory solid malignancy (histologically or cytologically documented)
• Has an Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1
• Has a minimum of one measurable tumor lesion
• Has acceptable hematologic and clinical chemistry laboratory values

Major Exclusion Criteria:

A patient is excluded if any of the following criteria apply:

• Has not recovered from AEs to at least grade 1 by CTCAE version 5.0 due to prior anti-cancer medications
• Has symptomatic, steroid-dependent or progressive brain metastasis/metastases
• Has a history of another primary malignancy, except for: a) Malignancy treated with curative intent and with no known active disease within 2 years prior to first dose of ATOR-1017, b) Adequately treated non-invasive basal skin cancer or squamous cell skin carcinoma, c) Adequately treated uterine cervical cancer stage 1B or less
• Has an autoimmune disorder requiring immune modulating treatment during the last 2 years
• Receives treatment with systemic immunosuppressant medication (except for inhaled and low dose systemic corticosteroids, i.e. ≤10 mg prednisolone or equivalent per day)
• Is a female patient who is pregnant or nursing