-  INCLUSION CRITERIA:

          -  Subjects with:

               -  histologically confirmed solid tumors (Phase I), OR

               -  histologically or cytologically confirmed SCLC (Phase II), OR

               -  histologically or cytologically confirmed extra-pulmonary small cell carcinomas
                  (Phase II).

          -  Age greater than or equal to 18 years. Because no dosing or adverse event data are
             currently available on the use of PLX038 in combination with rucaparib in participants
             <18 years of age, children are excluded from this study, but will be eligible for
             future pediatric trials.

          -  Subjects must have progressed on or after standard first-line systemic chemotherapy.

          -  Participants must have disease that is not amenable to potentially curative resection.

          -  Participants must have measurable disease per RECIST 1.1. See Section 6.3 for the
             evaluation of measurable disease.

          -  Participants with asymptomatic brain metastases and treated brain metastases are
             eligible.

          -  ECOG performance status less than or equal to 2.

          -  Adequate hematological function defined by:

               -  white blood cell (WBC) count greater than or equal to 3 x 10(9)/L,

               -  absolute neutrophil count (ANC) greater than or equal to 1.5 x10(9)/L,

               -  platelet count greater than or equal to 100 x 10(9)/L,

               -  Hgb greater than or equal to 9 g/ dL

          -  Adequate hepatic function defined by:

               -  a total bilirubin level less than or equal to 1.5 x ULN,

               -  an AST level less than or equal to 2.5xULN, (less than or equal to 5X ULN if
                  liver metastasis)

               -  an ALT level less than or equal to 2.5 xULN, (less than or equal to 5X ULN if
                  liver metastasis).

          -  Adequate renal function defined by:

               -  Creatinine OR Measured or calculated creatinine clearance (CrCl) (eGFR may also
                  be used in place of CrCl): < 1.5x institution upper limit of normal OR greater
                  than or equal to 45 mL/min/1.73 m(2) for participant with creatinine levels
                  greater than or equal to 1.5 X institutional ULN.

        Note: Creatinine clearance (CrCl) or eGFR should be calculated per institutional standard.

          -  The effects of the study treatment on the developing human fetus are unknown; thus,
             women of childbearing potential and men must agree to use adequate contraception
             (hormonal or barrier method of birth control; abstinence) prior to study entry, for
             the duration of study treatment and up to 6 months after the last dose of the study
             drug (s). Should a woman become pregnant or suspect she is pregnant while she or her
             partner is participating in this study, she should inform her treating physician
             immediately.

          -  Subjects must be able to understand and willing to sign a written informed consent
             document.

        EXCLUSION CRITERIA:

          -  Participants who are receiving any other investigational agents.

          -  Systemic anti-cancer treatment or major surgery within 2 weeks prior to enrollment.

          -  Radiotherapy within 24 hours prior to enrollment.

          -  Participants who require treatment with strong inhibitors or inducers of CYP3A or with
             UGT1A1 inhibitors during the planned period of investigational treatment with PLX038.

          -  Participants with known Gilbert s syndrome.

          -  Participants homozygous for the UGT1A1*28 variant allele with severely reduced UGT1A1
             activity.

          -  Participants with known HIV, HCV, HBV status on antiviral drugs are excluded due to
             the absence of previous experience with concurrent use of antiviral medications and
             the investigational drug product to be evaluated in the current study and possible for
             adverse pharmacokinetic and/or pharmacodynamic interactions.

          -  History of allergic reactions attributed to compounds of similar chemical or biologic
             composition to PLX038 or rucaparib.

          -  Uncontrolled intercurrent illness including, but not limited to, ongoing or active
             infection, symptomatic congestive heart failure, unstable angina pectoris, cardiac
             arrhythmia, or psychiatric illness/social situations that may impair the participants
             tolerance of study treatments.

          -  Pregnant women are excluded from this study because PEGSN38 and rucaparib potential
             for teratogenic or abortifacient effects are unknown. Because there is an unknown but
             potential risk for adverse events in nursing infants secondary to treatment of the
             mother with PEGSN38 and rucaparib, breastfeeding should be discontinued if the mother
             is treated with study drugs.