Study to Determine the Maximum Tolerated Dose (MTD) of PARPi 2X-121 Monotherapy and the MTD of Dovitinib in Combination With 2X-121 in Patients With Advanced Solid Tumors

Part 1

This part of the study will follow an accelerated titration method followed by a standard "3+3" design to determine the MTD of 2X-121. The MTD is defined as one dose level (cohort) below the dose in which dose limiting toxicities (DLTs) were observed in ≥ 33% of the participants.

The calculation of the sample size for this trial is based on the traditional 3 + 3 dose escalation scheme which is conducted as follows:

* Subjects are treated in cohorts of one (Cohort 1) or three (Cohorts 2-3) subjects, each receiving the same dose. For the assessment of a DLT, subjects are observed for 14 days. * In Cohort 1, if the one subject does not exhibit a DLT, the next cohort of three subjects will receive the next higher dose (Cohort 2). In Cohort 2, if none of the three subjects exhibits a DLT, the next cohort of three subjects will receive the next higher dose (Cohort 3). * Otherwise, if at least one subject of a cohort exhibits a DLT, a further cohort of three subjects is treated at the same dose level (cohort) without escalating the dose. * If exactly one out of the six subjects treated at this dose exhibits a DLT, the trial continues as planned at the next higher dose level (cohort). * If two or more subjects out of the six subjects treated at this dose exhibit a DLT, the dose escalation stops at that level and the next lower dose is considered as the MTD. When the escalation has stopped, additional subjects will be treated at the MTD to a total of six subjects.

Cohort escalation in Part 1 and Part 2 (i.e., the decision to progress from one cohort (dose level) to another) will not proceed until all of the following events have occurred:

1. All study subjects in a given cohort (dose level) have been enrolled, and 2. All such subjects have been followed for at least 14 days from the initiation of study treatment, and 3. The Investigator (PI), Sponsor's Medical Officer, and Medical Monitor have reviewed the available safety data, determined that none of the DLTs outlined below have occurred, and recommends further dose escalation

* Hematological

* Grade 4 neutropenia \[or Grade 3 neutropenia with fever (\>38.5 °C in axilla)\] for ≥ 7 days * Grade 4 thrombocytopenia (Grade 3 thrombocytopenia with bleeding) lasting \>7 days. * Other non-hematological toxicity

* Grade 3 fatigue, or a 2-point decline in Eastern Cooperative Oncology Group (ECOG) performance status that persists for \>7 days. * Nausea, vomiting or diarrhea that persists at Grade 3 or 4 despite maximal medical therapy. * Any Grade 3 or higher non-hematological laboratory abnormalities that require hospitalization.