Inclusion Criteria:

- Patients with histologically or cytologically confirmed breast cancer

- Distant metastases or locally advanced breast cancer

- Age ≥ 18 years

- ECOG performance ≤ 2

- Life expectancy of at least 6 months

- Written informed consent

- individual standard therapy according to guidelines

- Oral intake of trial medication possible

- Compliance with study procedures

- Women of childbearing potential: negative pregnancy test before start of medication

- Use of a highly effective method of birth control during intake of add-on therapy for
women of childbearing potential being sexually active

Exclusion Criteria:

- Allergy to artesunate or to other artemisinin derivatives

- Concurrent conditions interfering with patient safety

- Communication problems

- Concurrent participation in another clinical trial or 4 weeks prior to recruitment

- Participation in a clinical trial with an unapproved drug 6 months prior to
recruitment

- Sinus bradycardia, bradyarrhythmia

- AV-Block II° and III°

- QTc > 500 msec

- Previously known long QT-syndrome

- Concurrent intake of a medication with clinically relevant neurotoxicity or during 30
days prior to recruitment

- Relevant neurological symptoms which might complicate the evaluation of the
compatibility of the IMPD (f. e. cerebral metastases) or might be subject to
worsening during intake of the IMPD

- Radiotherapy 2 weeks prior of the intake of the IMPD

- Concurrent intake of supplements or any other medication with unapproved efficacy
f.e. vitamins, minerals or others (OTC)

- Pregnancy and lactation

- Ineffective mode of contraception in women of childbearing potential