Primary purpose of the clinical study is to evaluate the safety, biodistribution and radiation dosimetry of [131I]-SGMIB Anti-HER2 VHH1 in healthy volunteers and patients with HER2+ breast cancer.

Secondary purpose of the clinical study is to evaluate the tumor uptake of [131I]-SGMIB Anti-HER2 VHH1 in patients with HER2+ breast cancer.

Inclusion Criteria:

Subjects will only be included in the study if they meet all of the following criteria:

• Subjects who have given informed consent
• Subjects that agree not to drink alcoholic beverages or use any drugs during the study
• Subject with blood parameters within normal ranges
• Age: at least 18 years old

Patients will only be included in the study if they meet all of the following criteria:

• Patients who have given informed consent
• Patients that agree not to drink alcoholic beverages or use any drugs during the study
• Age: at least 18 years old
• Patients with local, locally advanced or metastatic HER2+ breast carcinoma as diagnosed on biopsied tissue by immunohistochemistry or fluorescence in situ hybridization (FISH).

Exclusion Criteria:

Patients will not be included in the study if one of the following criteria applies:

• Pregnant patients
• Breast feeding patients
• Patients with occupational exposure to ionizing irradiation
• Patients with previous thyroid disorders
• Patients that received radiolabeled compounds with a long half-life (>7h) for diagnostic or therapeutic purposes within the last 2 days.
• Patients with absolute contra-indications for thyroid blockage with potassium iodide.
• Patients with abnormal liver: ALT/AST > 2 times normal values; bilirubin > 1.5 time normal values.
• Patients with abnormal kidney function: < 50 ml/min/1,73 m2
• Patients with recent (< 1 week) gastrointestinal disorders (CTCAE v4.0 grade 3 or 4) with diarrhea as major symptom
• Patients with any serious active infection
• Patients who have any other life-threatening illness or organ system dysfunction, which in the opinion of the investigator would either compromise patient safety or interfere with the evaluation of the safety of the test radiopharmaceutical
• Patients who cannot communicate reliably with the investigator
• Patients who are unlikely to cooperate with the requirements of the study
• Patients at increased risk of death from a pre-existing concurrent illness
• Patients who participated already in this study
• Patients who participated in a previous trial with Anti-HER2 VHH1

Subjects will not be included in the study if one of the following criteria applies:

• Pregnant subjects
• Breast feeding subjects
• Subjects with occupational exposure to ionizing irradiation
• Subjects with clinical significant disease or on concomitant therapy (except contraception)
• Subjects with previous thyroid disorders
• Subjects that received radiolabeled compounds with a long half-life (>7h) for diagnostic or therapeutic purposes within the last 2 days.
• Subjects with absolute contra-indications for thyroid blockage with potassium iodide.
• Subjects with abnormal liver: ALT/AST > 2 times normal values; bilirubin > 1.5 time normal values.
• Subjects with abnormal kidney function: < 50 ml/min/1,73 m2
• Subjects with recent (< 1 week) gastrointestinal disorders (CTCAE v4.0 grade 3 or 4) with diarrhea as major symptom
• Subjects with any serious active infection
• Subjects who have any other life-threatening illness or organ system dysfunction, which in the opinion of the investigator would either compromise subject safety or interfere with the evaluation of the safety of the test radiopharmaceutical
• Subjects who cannot communicate reliably with the investigator
• Subjects who are unlikely to cooperate with the requirements of the study
• Subjects at increased risk of death from a pre-existing concurrent illness
• Subjects who participated already in this study
• Subjects who participated in a previous trial with Anti-HER2 VHH1