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Targeted Antibody Blocking by a Dual-Functional Conjugate of Antigenic Peptide and Fc-III Mimetics DCAF
Published on: September 17, 2019
High-affinity decoy protein, nFD164, with an inactive Fc region as a potential therapeutic drug targeting CD47
Zhihong Wang1, Naijing Hu1, Haitao Wang2
1State Key Laboratory of Toxicology and Medical Countermeasures, Beijing Institute of Pharmacology and Toxicology, Beijing 108500, China.
Abstract:
CD47, as an innate immune checkpoint molecule, is an important target of cancer immunotherapy. We previously reported that a high-affinity SIRPα variant FD164 fused with IgG1 subtype Fc showed a better antitumor effect than wild-type SIRPα in an immunodeficient tumor-bearing model. However, CD47 is widely expressed in blood cells, and the drugs targeting CD47 may cause potential hematological toxicity. Herein, we modified the FD164 molecule by Fc mutation (N297A) to inactivate the Fc-related effector function and named it nFD164. Moreover, we further studied the potential of nFD164 as a candidate drug targeting CD47, including the stability, in vitro activity, antitumor activity of single or combined drugs in vivo, and hematological toxicity in humanized CD47/SIRPα transgenic mouse model. The results show that nFD164 maintains strong binding activity to CD47 on tumor cells, but has weak binding activity with red blood cells or white blood cells, and nFD164 has good drug stability under accelerated conditions (high temperature, bright light and freeze-thaw cycles). More importantly, in the immunodeficient or humanized CD47/SIRPα transgenic mice bearing tumor model, the combination of nFD164 and anti-CD20 antibody or anti-mPD-1 antibody had a synergistic antitumor effect. Especially in transgenic mouse models, nFD164 combined with anti-mPD-1 significantly enhanced tumor suppressive activity compared with anti-mPD-1 (P < 0.01) or nFD164 (P < 0.01) as a single drug and had fewer hematology-related side effects than FD164 or Hu5F9-G4. When these factors are taken together, nFD164 is a promising high-affinity CD47-targeting drug candidate with better stability, potential antitumor activity, and improved safety profile.
Insights
A modified CD47-targeting drug, nFD164, shows improved stability and antitumor effects, with reduced hematological toxicity compared to previous versions. This makes nFD164 a promising candidate for cancer immunotherapy.
Area of Science:
- Immunology
- Oncology
- Pharmacology
Background:
- CD47 is an innate immune checkpoint molecule and a key target in cancer immunotherapy.
- Previous high-affinity SIRPα variants like FD164 showed antitumor effects but raised concerns about hematological toxicity due to CD47 expression on blood cells.
Purpose of the Study:
- To evaluate nFD164, a modified FD164 with inactivated Fc effector function, as a potential CD47-targeting cancer therapeutic.
- To assess the stability, in vitro activity, in vivo antitumor efficacy (single and combination therapy), and hematological safety of nFD164.
Main Methods:
- Fc mutation (N297A) was introduced into FD164 to create nFD164.
- Drug stability was tested under accelerated conditions.
- In vitro binding activity to CD47 on tumor cells and blood cells was assessed.
- In vivo antitumor activity was evaluated in immunodeficient and humanized CD47/SIRPα transgenic mouse models, alone and in combination with anti-CD20 or anti-mPD-1 antibodies.
- Hematological toxicity was assessed in a humanized mouse model.
Main Results:
- nFD164 demonstrated strong binding to tumor cell CD47 but weak binding to red and white blood cells.
- The drug exhibited good stability under accelerated storage conditions.
- Combination therapy with nFD164 and anti-CD20 or anti-mPD-1 antibodies showed synergistic antitumor effects in mouse models.
- nFD164 combined with anti-mPD-1 significantly enhanced tumor suppression compared to single agents in transgenic models.
- nFD164 exhibited fewer hematology-related side effects than FD164 or Hu5F9-G4.
Conclusions:
- nFD164 is a promising high-affinity CD47-targeting drug candidate.
- nFD164 offers improved drug stability and a potentially better safety profile with reduced hematological toxicity.
- The combination of nFD164 with other immunotherapies, like anti-mPD-1, demonstrates significant potential for synergistic antitumor activity.
