177Lu–DO3A–HSA–ZEGFR:1907: characterization as a potential radiopharmaceutical for radionuclide therapy of EGFR-expressing head and neck carcinomas

Abstract

Epidermal growth factor receptor 1 (EGFR) is an attractive target for radionuclide therapy of head and neck carcinomas. Affibody molecules against EGFR (Z(EGFR)) show excellent tumor localizations in imaging studies. However, one major drawback is that radiometal-labeled Affibody molecules display extremely high uptakes in the radiosensitive kidneys which may impact their use as radiotherapeutic agents. The purpose of this study is to further explore whether radiometal-labeled human serum albumin (HSA)-Z(EFGR) bioconjugates display desirable profiles for the use in radionuclide therapy of EGFR-positive head and neck carcinomas. The Z(EFGR) analog, Ac-Cys-Z(EGFR:1907), was site-specifically conjugated with HSA. The resulting bioconjugate 1,4,7,10-tetraazacyclododecane-1,4,7-triacetic acid (DO3A)-HSA-Z(EGFR:1907) was then radiolabeled with either (64)Cu or (177)Lu and subjected to in vitro cell uptake and internalization studies using the human oral squamous carcinoma cell line SAS. Positron emission tomography (PET), single photon emission computed tomography (SPECT), and biodistribution studies were conducted using SAS-tumor-bearing mice. Cell studies revealed a high (8.43 ± 0.55 % at 4 h) and specific (0.95 ± 0.09 % at 4 h) uptake of (177)Lu-DO3A-HSA-Z(EGFR:1907) as determined by blocking with nonradioactive Z(EGFR:1907). The internalization of (177)Lu-DO3A-HSA-Z(EGFR:1907) was verified in vitro and found to be significantly higher than that of (177)Lu-labeled Z(EFGR) at 2-24 h of incubation. PET and SPECT studies showed good tumor imaging contrasts. The biodistribution of (177)Lu-DO3A-HSA-Z(EGFR:1907) in SAS-tumor-bearing mice displayed high tumor uptake (5.1 ± 0.44 % ID/g) and liver uptake (31.5 ± 7.66 % ID/g) and moderate kidney uptake (8.5 ± 1.08 % ID/g) at 72 h after injection. (177)Lu-DO3A-HSA-Z(EGFR:1907) shows promising in vivo profiles and may be a potential radiopharmaceutical for radionuclide therapy of EGFR-expressing head and neck carcinomas.

Tumour targeting with radiometals for diagnosis and therapy

“…Biodistribution studies showed long retention of the radiopharmaceutical in the tumour and good tumour contrast in SPECT images. 177 Lu-DO3A-HSA-Z EGFR:1907 showed lower uptake in the kidneys compared to the 177 Lu-DO3A-Z EGFR:1907 alone, 83 but instead high and persistent liver uptake was seen which may suggest the introduction of such a large protein has influenced the pharmacokinetic and metabolic behaviour of the radiopharmaceutical towards the liver.…”

“…In general, biological half-life of antibody fragments is inversely proportional to the molecular weight of the molecule. With their reduced size antibody fragments exhibit faster blood clearance (o10 h for an Affibody compared to 3-4 weeks for the full mAb), 83 which means faster acquisition times for imaging purposes, and lower non-specific radiotoxicity for therapeutic isotopes. In turn, the isotopes used with antibody fragments can have shorter half-lives.…”

“…72 A recent study implemented the anti-EGFR Affibody Z EGFR:1907 in a 177 Lu-radiotherapeutic. 83 In previous studies radiolabelled-Z EGFR:1907 showed…”

Influence of protein properties and protein modification on biodistribution and tumor uptake of anticancer antibodies, antibody derivatives, and non‐Ig scaffolds

“…HSA conjugation and subsequent biodistribution studies have been performed with affibodies targeting EGFR ( 177 Lu-DO3A-HSA-Z EGFR:1907 ) and HER2 ( 111 In-DOTA-HSA-Z HER2:342 ) in mice. 193,194 At 4 hr after injection blood levels were, respectively, 19.07 ± 1.05% ID/g and 20.11 ± 3.5% ID/g, which are much higher compared to radiolabeled affibodies that do not bind albumin in vivo, typically <2.4% ID/g ( Table 5). High blood levels of both HSA-conjugated affibodies resulted in high uptake in normal organs, especially in the liver.…”

“…However, due to the fact that antialbumin affibodies and VHHs are small in size, the effect of increasing the protein size by introducing antialbumin domains is not discussed in this section. HSA conjugation and subsequent biodistribution studies have been performed with affibodies targeting EGFR ( 177 Lu‐DO3A‐HSA‐Z EGFR:1907 ) and HER2 ( 111 In‐DOTA‐HSA‐Z HER2 :342 ) in mice . At 4 hr after injection blood levels were, respectively, 19.07 ± 1.05% ID/g and 20.11 ± 3.5% ID/g, which are much higher compared to radiolabeled affibodies that do not bind albumin in vivo, typically <2.4% ID/g (Table ).…”