Inclusion Criteria:

          1. Phase 1b: Histologically or cytologically confirmed recurrent/metastatic solid cancer
             patients with no available standard treatment and be expected to have the anti-tumor
             effect with combination of GC1118 and irinotecan or GC1118 and FOLFIRI by
             investigator's judgement Phase 2a: Historically or cytologically confirmed, 1)
             EGFR-positive, KRAS/NRAS and BRAF wild type recurrent/metastatic colorectal cancer
             patients who failed first line chemo or targeted therapies (fluoropyrimidine-based or
             oxaliplatin containing chemotherapy) or whose disease were progressed within 6 months
             after the last dose of above mentioned treatments; Disease progression during
             treatment or within 6 months after completion of adjuvant/neoadjuvant chemotherapy is
             also considered as first line treatment failure 2) Medically documented non-HER2
             overexpression (HER2 3+ or HER2+/FISH+) and EGFR 2+ or 3+ expressing
             recurrent/metastatic gastric cancer patients who failed (radiologically progressed)
             second line chemo or targeted therapies

          2. Male of female, 19 years of age or older

          3. ECOS PS 0 or 1

          4. Life expectancy of 3 months or longer

          5. Phase 2a: Presence of at least one measurable lesion according to the RECIST criteria
             v1.1

          6. Phase 2a: Demonstration of each cohort requirements including EGFR positive, KRAS/NRAS
             and BRAF wild type, EGFR 2+ or 3+ expression, and etc.

          7. Adequate bone marrow function, renal function, and hepatic function

          8. All AEs caused by previous anticancer therapies, including surgery, chemotherapy, and
             radiation therapy,have recovered to CTCAE grade 1 or below (except alopecia)

        Exclusion Criteria:

          1. Any of the following medical histories 1) Major surgery, open biopsy, or significant
             traumatic injury within 4 weeks prior to the first investigational products
             administration or adverse events are not resolved from such procedure or injury 2)
             Other malignancies (exception; any of the following status are eligible) i. Disease
             free for 3 years or completely resected non-melanoma skin cancer ii. Successfully
             treated in carcinoma in situ (CIS) iii. Ta, CIS, or T1a staged superficial bladder
             cancer which is completely cured iv. Papillary thyroid cancer which is not being
             progressed without ongoing treatment v. Prostate cancer which is surgically or
             medically cured and is not likely to recur within 2 years

          2. Any of the following concurrent disease 1) Known brain metastasis 2) Active infection
             requiring systemic anti-microbial therapy 3) Human immunodeficiency virus infection or
             active hepatitis B or C 4) Chronic inflammatory bowel disease 5) Clinically
             significant interstitial lung disease or pulmonary fibrosis 6) Clinically significant
             hepatic disease including decompensated liver cirrhosis, etc

          3. Any of the following medication histories 1) Phase 2a recurrent/metastatic colorectal
             cancer: Treated with irinotecan containing regimen as first line treatment for
             recurrent/metastatic cancer 2) Phase 2a: Prior EGFR targeting antibody therapy 3)
             Received chemotherapy, immunotherapy, hormone therapy, radiotherapy within 3 weeks
             (within 6 weeks in case of nitrosourea or mitomycin-c) prior to first investigational
             products administration (In phase 2, radiotherapy within 3 weeks is not restricted
             unless the site is measurable lesion) 4) Ongoing or requiring the prohibited
             medications including immunotherapy, chemotherapy, hormone therapy, or etc. 5)
             Received other investigational drugs with 4 weeks prior to this investigational
             products adminstration

          4. Medically or psychologically inappropriate conditions for study participation by
             investigator's judgment

          5. Contraindication for FOLFIRI (or irinotecan) therapy

          6. Pregnant, possibly pregnant, or lactating women (Women of child bearing potential must
             test negative for pregnancy within 3 days prior to Cycle1 Day1

          7. Refusal to use the following appropriate contraceptives during the clinical study
             period and for 6 months after the last adminstration of investigational products 1)
             Implanted intrauterine device or intrauterine system 2) Double barrier methods (Both
             of condom (for mate) and diaphragm, vaginal sponge, or cervical cap (for female)
             should be used with spermicide) 3) Surgical sterilization (vasectomy, tubal ligation,
             etc.)

          8. Any other inappropriate conditions for study participation at investigator's
             discretion