Multicenter, open-label, single-arm, phase II, pilot study. The screening period was up to 4 weeks and treatment took place over 20 weeks per patient. Five visits per patient were performed including: Visit 1 at week -4 to -1 (screening), Visit 2 at week 0 (baseline), Visit 3 at week 4, Visit 4 at week 12, and Visit 5 at week 20 (end of study). There was no follow-up period.

This was a multicenter, open-label, single-arm, phase II, pilot study to evaluate the efficacy and safety of apremilast involving 21 patients with PPP. The screening period was up to 4 weeks and treatment took place over 20 weeks per patient. No follow up period took place. No extension was done.

Recruitment period was 4 months; hence study duration from first patient in to last patient out was approximately 9 months. About 4-6 patients per center were recruited, assuming enrolment of both genders with distribution according to prevalence of condition.

Patient recruitment took place at 5 centers in Germany. The investigators had relevant expertise in diagnosing and treating PPP or were specialized in dermatology. Patients were enrolled until approximately 20 patients were included into the study. One drop-out was replaced during the recruitment phase.

Five visits per patient were performed including:

• Visit 1 at week -4 to -1 (screening)
• Visit 2 at week 0 (baseline)
• Visit 3 at week 4
• Visit 4 at week 12
• Visit 5 at week 20 (end of study)

After the end of study participation the investigator ensured that the patient received a suitable therapy appropriate to patient's condition.

Inclusion Criteria:

• Male and female patients aged 18 years or more at screening visit.

• Patients with chronic PPP (disease history of at least 6 months of diagnosis), who were eligible for treatment with systemic therapy defined as having PPP inadequately controlled by topical treatment and/or phototherapy and/or previous systemic therapy

• Patients with chronic moderate to severe PPP defined as patients with a PPPASI ≥12 with or without concomitant plaque-type psoriasis

• Negative result of a urine pregnancy test taken at screening and at baseline for all women, except those who were surgically sterile or at least 1 year postmenopausal (i.e. at least 12 consecutive months with amenorrhea without other known or suspected medical cause)

• Willingness and capability of using a highly effective contraceptive measures from Screening visit until the end of at least one menstrual cycle (but not less than 28 days) following discontinuation of apremilast as defined below:

  • Female patient of childbearing potential (fertile, following menarche and until becoming post- menopausal unless permanently sterile) using a highly effective method of contraception OR female patients of non-childbearing potential (surgically sterilized [e.g. hysterectomy, bilateral salpingectomy and bilateral oophorectomy] or postmenopausal)

  • Male patient, and their female partner of childbearing potential, using a highly effective method of contraception

  • Adequate contraceptive method defined as:

    • A method with less than 1% failure rate (e.g. permanent sterilization, hormone implants, hormone injections, some intrauterine devices, or vasectomized partner) OR
    • The use of two methods of contraception (e.g. one barrier method [condom, diaphragm or cervical/vault caps] with spermicide and one hormonal contraceptive [e.g. combined oral contraceptives, patch, vaginal ring, injectables and implants])

• Patient was capable of understanding and giving written, voluntary informed consent before study screening.

• Willingness and capability of complying with all study procedure requirements, as per the Investigator's judgment (e.g. patient able to swallow the apremilast tablets, blood sampling).

Exclusion Criteria:

• General:

  • Pregnant or breast-feeding women
  • Current or history of psychiatric disease that would interfere with the ability to comply with the study protocol or give informed consent
  • Patients known to have had a substance abuse (drug or alcohol) problem within the previous 12 month
  • Individuals who were involved in the organization of the study
  • Patients who were in any way dependent on the investigator
  • Patients who were participating in a clinical study
  • Relatives, partner or staff of any clinical site personnel

• Disease-related:

  • Evidence of skin conditions (e.g. eczema) other than PPP/psoriasis that would interfere with evaluations of the effect of study medication on PPP or psoriasis.

  • Laboratory values from routine blood test taken within the 8 weeks prior to screening with any of the following:

    • Serum creatinine >1.4 x upper limit of normal (ULN) for age and gender
    • Estimated Glomerular Filtration Rate (eGFR) <30 mL/min/1.73m2 according to the Chronic Kidney Disease-Epidemiology Collaboration (CKD-EPI) equation

  • Pustular psoriasis lesions on the part of body other than hands or feet

  • Significant concurrent medical conditions at the time of screening, including:

    • Risk factors for renal toxicity (renal inflammation)
    • Severe hepatic dysfunction
    • Unstable angina pectoris
    • Uncompensated congestive heart failure
    • Severe pulmonary disease requiring hospitalization or supplemental oxygen therapy
    • Immunodeficiency disorders: primary or secondary
    • Known positive human immunodeficiency virus (HIV) test result, hepatitis B surface (HBS) antigen or hepatitis C virus (HCV) test result
    • Uncontrolled insulin-dependent diabetes mellitus
    • Cancer or history of cancer (except for resected cutaneous basal cell or squamous cell carcinoma) in the last 5 years
    • Open cutaneous ulcers

  • Any condition that, in the judgment of the investigator, might cause this study to be detrimental to the patient.

• Medication-related:

  • Ultraviolet B (UVB) therapy, topical steroids, topical calcineurin inhibitors, topical Vitamin A or D analog preparations, or anthralin within 14 days of baseline. Exceptions: low potency topical corticosteroids (class I and II, according to European classification for potency of topical corticosteroids) were allowed as therapy for the face, groin, axillae in accordance with the manufacturer's suggested usage dose
  • Psoralen plus ultraviolet A radiation (PUVA), ciclosporin, acitretin, alitretinoin, alefacept (Amevive®), anakinra (Kineret®), systemic corticosteroids, methotrexate, fumaric acids or any other systemic anti- psoriasis therapy within 28 days of baseline
  • Prior (within the last 2 years) or concomitant use of antipsoriatic biologic therapy with TNF-alpha blocker and/or ustekinumab and/or ixekizumab and/or secukinumab and/or brodalumab and/or guselkumab
  • Concomitant use of strong cytochrome P450 3A4 (CYP3A4) enzyme inductors (e.g. rifampicin, phenobarbital, carbamazepin, phenytoin and St. John's wort)
  • Use of an investigational drug within 4 weeks prior to baseline or 5 pharmacokinetic/pharmacodynamics half-lives (whichever is longer)
  • Prior treatment with apremilast/Otezla®
  • Receipt of any live (attenuated) vaccine within 28 days prior to baseline
  • Concomitant use of any other PDE4 inhibitor
  • Patients with hereditary problems of galactose intolerance, lapp lactase deficiency or glucose-galactose malabsorption
  • For patients with skin biopsy samples taken: patients with clinically relevant coagulation disorders or medication or known hypersensitivity against local anesthetics.

All AEs were monitored/assessed from baseline (Visit 2, onset of treatment) until the patient's last study visit (i.e., up to 20 weeks). All SAEs were monitored/assessed upon ICF signature (Visit 1) until 30 days after the patient had stopped study participation (i.e., up to 24 weeks plus 30 days).

The date of onset, intensity, relationship of the AE to study drug, action(s) taken, seriousness, time course, duration and outcome were recorded.

The interpretation of APLANTUS study is limited by the short-term 20-week treatment period and the size of the population.