A lyophilised formulation comprising: (i) an active pharmaceutical ingredient (API); (ii) a buffering agent; and (iii) a lyoprotectant; wherein the API is an imaging agent comprising at least one cMet binding peptide, suitable for optically imaging the mammalian body, the imaging agent comprising a compound of Formula I: wherein: Z 1 is attached to the N-terminus of cMBP, and is H or M IG ; Z 2 is attached to the C-terminus of cMBP, and is OH, NH 2 , OB c or M IG ; wherein B c is a biocompatible cation; cMBP is a cMet binding cyclic peptide of 17 to 30 amino acids, which comprises the amino acid sequence (SEQ-1): wherein: Xaa 1 is Asn, His or Tyr; Xaa 2 is Gly, Ser, Thr or Asn; Xaa 3 is Thr or Arg; Xaa 4 is Ala, Asp, Glu, Gly or Ser; Xaa 5 is Ser or Thr; Xaa 6 is Asp or Glu; and Cys a-d are each cysteine residues such that residues a and b as well as c and d are cyclised to form two separate disulphide bonds; M IG is a metabolism inhibiting group, which is a biocompatible group that inhibits or suppresses in vivo metabolism of the peptide; L is a synthetic linker group of formula -(A)m- wherein each A is independently -CR 2 -, -CR=CR-, -C≡C-, -CR 2 CO 2 -, - CO 2 CR 2 -, -NRCO-, -CONR-, -NR(C=O)NR-, -NR(C=S)NR-, - SO 2 NR-, -NRSO 2 -, CR 2 OCR 2 -, -CR 2 SCR 2 -, CR 2 NRCR 2 -, a C 4-8 cycloheteroalkylene group, a C 4-8 cycloalkylene group, a C5-12 arylene group, a C 3-12 heteroarylene group, an amino acid, a sugar or a monodisperse polyethyleneglycol (PEG) building block; each R is independently chosen from H, C 1-4 alkyl, C 2-4 alkenyl, C 2-4 alkynyl, C 1-4 alkoxyalkyl or C 1-4 hydroxyalkyl; m is an integer of value 1 to 20; n is an integer of value 0 or 1; IM is an optical reporter imaging moiety suitable for imaging the mammalian body using light of violet to near-infrared wavelength (400 to 1,200 nm); wherein the formulation comprises from approximately 4 to approximately 12 % by weight API, from approximately 3 to approximately 35 % by weight buffering agent, and from approximately 56 to approximately 91 % by weight lyoprotectant; and wherein the formulation, when reconstituted, has a pH of between approximately pH 6.8 and approximately pH 9. (i) an active pharmaceutical ingredient (API); (ii) a buffering agent; and (iii) a lyoprotectant; Z 1 is attached to the N-terminus of cMBP, and is H or M IG ; Z 2 is attached to the C-terminus of cMBP, and is OH, NH 2 , OB c or M IG ; cMBP is a cMet binding cyclic peptide of 17 to 30 amino acids, which comprises the amino acid sequence (SEQ-1): wherein: Xaa 1 is Asn, His or Tyr; Xaa 2 is Gly, Ser, Thr or Asn; Xaa 3 is Thr or Arg; Xaa 4 is Ala, Asp, Glu, Gly or Ser; Xaa 5 is Ser or Thr; Xaa 6 is Asp or Glu; and Cys a-d are each cysteine residues such that residues a and b as well as c and d are cyclised to form two separate disulphide bonds; wherein: Xaa 1 is Asn, His or Tyr; Xaa 2 is Gly, Ser, Thr or Asn; Xaa 3 is Thr or Arg; Xaa 4 is Ala, Asp, Glu, Gly or Ser; Xaa 5 is Ser or Thr; Xaa 6 is Asp or Glu; M IG is a metabolism inhibiting group, which is a biocompatible group that inhibits or suppresses in vivo metabolism of the peptide; L is a synthetic linker group of formula -(A)m- wherein each A is independently -CR 2 -, -CR=CR-, -C≡C-, -CR 2 CO 2 -, - CO 2 CR 2 -, -NRCO-, -CONR-, -NR(C=O)NR-, -NR(C=S)NR-, - SO 2 NR-, -NRSO 2 -, CR 2 OCR 2 -, -CR 2 SCR 2 -, CR 2 NRCR 2 -, a C 4-8 cycloheteroalkylene group, a C 4-8 cycloalkylene group, a C5-12 arylene group, a C 3-12 heteroarylene group, an amino acid, a sugar or a monodisperse polyethyleneglycol (PEG) building block; each R is independently chosen from H, C 1-4 alkyl, C 2-4 alkenyl, C 2-4 alkynyl, C 1-4 alkoxyalkyl or C 1-4 hydroxyalkyl; m is an integer of value 1 to 20; n is an integer of value 0 or 1; IM is an optical reporter imaging moiety suitable for imaging the mammalian body using light of violet to near-infrared wavelength (400 to 1,200 nm); <EOS>