A Multi-center, Randomized, Double-blind, Placebo-controlled, Multiple Ascending Dose Study of the Safety, Tolerability, and Pharmacokinetics of Subcutaneously Delivered ASLAN004 in Adults With Moderate-Severe Atopic Dermatitis

Inclusion Criteria: 1. Adult patients who are of or older than the legal age in participating countries, who are able to read and understand, and willing to sign the informed consent form. 2. Willing and able to comply with clinic visits and study-related procedures. 3. Have a clinical diagnosis of chronic atopic dermatitis (per Eichenfield revised criteria of Hanifin and Rajka) that has been present for at least 3 years before the screening visit. 4. Have an IGA score of ≥3 at the screening and baseline visits. 5. Have ≥10% body surface area (BSA) of AD involvement at the screening and baseline visits. 6. Have an EASI score ≥16 at the screening and baseline visits. 7. Have a history of inadequate response to a stable (≥1 month) regimen of topical corticosteroids or calcineurin inhibitors as treatment for AD within 3 months before the screening visit. 8. Have applied a stable dose of an additive, basic, bland topical emollient (moisturizer) twice daily for at least 7 days before Randomization. Exclusion Criteria: 1. Have received previous treatment with therapeutic agents targeting ligand or receptors of IL-4 or IL-13, including but not limited to dupilumab, lebrikizumab, or tralokinumab. 2. Have inadequate organ and hematological function at the screening visit (as per protocol) 3. Have uncontrolled blood pressure at the screening visit based on clinical judgment of the Investigator. 4. Have a chest radiograph at Screening or within 3 months before the screening visit with results consistent with prior or current tuberculosis infection (including but not limited to apical scarring, apical fibrosis, or multiple calcified granuloma). This does not include non caseating granulomata. QuantiFERON gold standard may be conducted per standard practice at the site. 5. Have a known history of Human Immunodeficiency Virus (HIV), Hepatitis B or Hepatitis C infection or positive Hepatitis B surface antigen (HBsAg) or Hepatitis B core antibody HBcAb), positive Hepatitis C antibody (HCV) at the screening visit. 6. Have a known or suspected history of immunosuppression, including history of invasive opportunistic infections such as tuberculosis, histoplasmosis, listeriosis, coccidioidomycosis, candidiasis, pneumocystis jiroveci, aspergillosis despite infection resolution; JC virus (progressive multifocal leukoencephalopathy). 7. Have received treatment with topical corticosteroids, tacrolimus, and/or pimecrolimus within 1 week before Randomization. 8. Have received treatment with prescription moisturizers or moisturizers containing additives such as ceramide, hyaluronic acid, urea, or filaggrin degradation products (eg., Atopiclair®, MimyX®, Epicerum®, Cerave®, etc) within 1 week before Randomization. 9. Have had systemic treatment for AD with cyclosporine, mycophenolate-mofetil, interferon gamma (IFN-γ), phototherapy (narrow band ultraviolet B \[NBUVB\], ultraviolet B \[UVB\], ultraviolet A1 \[UVA1\], psoralen + ultraviolet A \[PUVA\]), azathioprine, or methotrexate within 4 weeks before Randomization. 10. Have had treatment with leukotriene inhibitors within 4 weeks before Randomization. 11. Have had treatment with systemic corticosteroids within 4 weeks before Randomization. 12. Have had treatment with small molecule investigational drugs (eg., tofacitinib) within 8 weeks before Randomization. 13. Have had treatment with biologics other than those targeting ligand or receptors of IL-4 or IL-13 within 8 weeks before Randomization. 14. Have had treatment with live attenuated vaccine within 8 weeks before Randomization. 15. Have had treatment with allergen immunotherapy within 6 months before Randomization. 16. Have had a regular use (more than 2 visits per week) of a tanning booth/parlor within 4 weeks of the screening visit. 17. Requirement of more than 2 bleach baths per week during study participation. 18. Have chronic or acute infection requiring treatment with systemic antibiotics, antivirals, antiparasitics, antiprotozoals, or antifungals within 4 weeks before the screening visit, or superficial skin infections within 1 week before the screening visit. 19. Presence of skin comorbidities that may interfere with study assessments. 20. Have a clinically significant history or evidence of any active or suspected parasitic infection (other than treated trichomoniasis) within the 4 weeks before Randomization or has travelled within the past 3 months of Randomization to areas of high parasitic exposure (based on Centers for Disease Control and Prevention \[CDC\] travel notice alert Level 2 and warning Level 3). 21. Have a history of malignancy within 5 years before Randomization with the following exceptions: patient with a history of cured in situ carcinoma of the cervix, and/or non-metastatic squamous or basal cell carcinoma of the skin are allowed. 22. Have any medical or psychiatric condition which, in the opinion of the Investigator or the Sponsor's Medical Monitor, would place the patient at risk, interfere with participation in the study, or interfere with the interpretation of study results. 23. Have a history of alcohol or drug abuse within 2 years of the screening visit. 24. Have scheduled or anticipate any surgical procedure during study participation and/or hospitalization for any reason within 60 days of Screening. 25. Pregnant or breastfeeding women. 26. Patients who are unwilling to use adequate birth control, if of reproductive potential and sexually active. For females, adequate birth control implies: use of hormonal contraceptives, intrauterine devices (IUD), or double barrier contraception (condom + diaphragm, condom or diaphragm + spermicidal gel or foam). For males, adequate birth control implies: use of double barrier contraception (condom + diaphragm, condom or diaphragm + spermicidal gel or foam). Abstinence is also accepted if this is the normal habit of the patient. 27. Patients who are dependent on prescription moisturizers.