Inclusion Criteria:

1. Patients with advanced or metastatic colorectal cancer (mCRC) and non-mutated
(wild-type) KRAS who are planned to receive treatment with panitumumab monotherapy
after failure of fluoropyrimidine-, oxaliplatin-, and irinotecan-containing
chemotherapy regimens and without prior treatment with epidermal growth factor
receptor (EGFR) antibody

2. Man or woman 18 years of age or older

3. Signed and dated informed consent before the start of specific protocol procedures

4. ECOG (Eastern Cooperative Oncology Group) performance status of 0, 1, or 2

5. Bilirubin ≤ 1.5 x ULN, SGOT/SGPT ≤ 2.5 x ULN, AP ≤ 3 x ULN if no evidence of liver
metastases or Bilirubin ≤ 3 x ULN, SGOT/SGPT ≤ 5 x ULN, AP ≤ 5 x ULN if evidence of
liver metastases

6. Women of child-bearing potential have to use adequate highly effective methods of
contraception . Since doxycyline may reduce efficacy of hormonal contraceptives,
women of child-bearing potential have to use double-barrier methods within 4 weeks
before first intake of study medication, during study participation and at least 6
weeks after last intake of study medication even if using hormonal contraceptives
Women are considered to be of child-bearing potential unless they are ≥ 50 years old
and for more than 2 years amenorrheic or unless they are surgically sterile.

Exclusion Criteria:

1. Absence of any of the above-listed inclusion criteria

2. Any serious medical condition or psychiatric illness that would interfere with the
patient's ability to sign the informed consent form.

3. Allergic reaction to one of the medications to be used

4. Subject allergic to panitumumab or any components of the panitumumab formulation or
treatment regimen

5. Prior treatment with EGFR antibody

6. CYP3A4 enzyme inducers, inhibitors, and substrates (eg, phenytoin, phenobarbital,
carbamazepine, ketoconazole, rifampicin, rifabutin, and St. John's Wort) ≤ 2 weeks
before randomization (itraconazole should be used with caution)

7. Subjects with hypersensitivity to doxycycline, other tetracyclines, or ingredients of
doxycycline capsules

8. Systemic treatment with antibiotics which was completed less than 7 days prior to
randomization

9. Pregnant and/or breast-feeding women

10. Active participation in other clinical studies in the previous 4 weeks

11. Serious liver function disorders

12. History of, or evidence of, interstitial pneumonitis or pulmonary fibrosis

13. Person who has been committed to an institution by virtue of an order issued either
by the judicial or the administrative authorities.