Overview of the Antibody Drug Conjugate Landscape Godfrey Amphlett WCBP CMC Strategy Forum January 24, 2010

Transcription

1 Overview of the Antibody Drug Conjugate Landscape Godfrey Amphlett WCBP CMC Strategy Forum January 24, 2010

2 Outline of Talk What is an Antibody Drug Conjugate (ADC)? Rationale for developing ADC s What types of ADC s are being investigated clinically? Analytical challenges in developing ADC s Regulatory considerations in developing ADC s Robustness of conjugate manufacturing processes

3 What is an Antibody Drug Conjugate (ADC)? The focus of this meeting is on antibodies conjugated to small molecule cytotoxic agents We will not be considering: Pegylated proteins Antibodies conjugated to radionuclides (e.g. Y-90, I-131) Antibodies conjugated to protein toxins (e.g. bouganin, gelonin, saporin, ricin)

4 Rationale for Antibody Drug Conjugates Some small molecule drugs have high systemic toxicity, e.g. chemotherapy drugs used for cancer treatment Antibodies can target particular cells (e.g. antigenpositive tumor cells) quite selectively Covalently linking antibodies to small molecule drugs can target the drug and reduce systemic toxicity With antibodies that have biological activity, conjugation may increase their effectiveness

5 Mechanism of Action of an ADC Targeted Antibody Payload (TAP) technology The antibody of the conjugate recognizes and binds to antigens on the surface of the cancer cell The immunoconjugate is internalized Inside the tumor cell, the cytotoxic agent is released and kills the cell Immunoconjugates are inactive outside the tumor cell

6 Conjugation Leads to Superior Preclinical Properties In vitro cytotoxicity In vivo efficacy Surviving fraction of cells Namalwa (antigen-negative) COLO 205 (antigen-positive) Mean Tumor Volume (mm 3 ) PBS control huc242 antibody huigg1-dm 4 (non-binding) unconjugated DM4 huc242-dm4 [huc242-dm4], M 5 day continuous exposure Cell killing activity is selective for antigenpositive cells even though both cell lines are equally sensitive to the free drug Days (post inoculation) SCID mice bearing established subcutaneous COLO 205 xenografts were treated with huc242-dm4 12 mg/kg) as a single bolus IV injection DM4 conjugation confers potent anti-tumor activity to tumor-targeting antibody

7 ADC s can also show impressive clinical efficacy: example of IMGN901 (anti-cd56-dm1) Merkel cell carcinoma (metastatic) 3 of 6 patients had marked response: 1 complete remission (ongoing > 4 years); 1 patient with continued improvement after one treatment cycle (PR tracking to potential CR); 1 patient with sustained stable disease Small-cell lung cancer (metastatic) 25% CBR Multiple myeloma Extended response in patients previously treated with a number of therapies Pre-IMGN901 Feb. 09 Post-IMGN901 Mar. 09 Post-IMGN901 Aug. 09 Metastatic Merkel cell carcinoma: median survival of 6.8 months and no approved treatments PR=Partial response (RECIST criteria) CR=Complete response (RECIST criteria) CBR = Clinical benefit rate = objective responses + stable disease lasting 3 months

8 Antibody Drug Conjugates in the Clinic Calicheamicin based (Pfizer, formerly Wyeth) Gemtuzumab Ozogamicin, Mylotarg (anti-cd33) currently the only ADC approved for marketing. AML CMC-544 (anti-cd22). NHL Maytansinoid based (ImmunoGen) T-DM1 (anti HER 2, Genentech/Roche). Breast cancer IMGN901 (anti-cd56). SCLC, Multiple Myeloma IMGN388 (anti-integrin). Solid tumors SAR3419 (anti-cd19, sanofi-aventis). NHL BIIB015 (anti-cripto, Biogen Idec). Solid tumors BT-062 (anti-cd138, Biotest). Multiple myeloma

9 Antibody Drug Conjugates in the Clinic (contd.) Auristatin based (Seattle Genetics) SGN-35 (anti-cd30). Hodgkin Lymphoma CR-011 (anti-gpnmb, Curagen). Melanoma PSMA ADC (anti-psma, Progenics). Prostate MED 1547 (anti-epha2, Astra Zenica/Medimmune). Solid tumors MN-IC (anti-mn, Bayer). Solid tumors SGN-75 (anti-cd70). Hematologic/solid tumors Undisclosed cytotoxic agent (BMS/Medarex) MDX1203 (anti-cd70). Renal, NHL Other cytotoxic agents (e.g. in preclinical development) Doxorubicin based Duocarmycin based Paclitaxel based

10 Structure of a Representative Antibody-Maytansinoid Conjugate The cytotoxic agent (e.g. DM4) is attached to an antibody through a linker (e.g. SPDB) that is bound to the side chains of lysine residues. MAb Linker DM4 The final conjugate product contains a defined average number (n) of maytansinoid molecules per antibody molecule. MAb Linker Cytotoxic Agent (Common to all ADC s)

11 Examples of Bifunctional Linkers Used to Make Antibody Maytansinoid Conjugates O O N S S O N O SPDB Cleavable Disulfide O N O O N O SMCC - Noncleavable O O SSPy or Maleimide reacts with Cytotoxic Agent NHS reacts with protein

12 Attachment of the Bifunctional Linker to the Antibody Determines where cytotoxic agents will be attached key step in manufacturing Linkage through amide bond to Lysine N-hydroxysuccinimide (NHS) reactive group on linker reacts with accessible and reactive Lysine residues on antibody Linkage through thioether bond to Cysteine Maleimide reactive group on linker reacts with Cysteine From S-S bonds after reduction of the antibody Engineered Cysteine residues

13 Generalized Conjugation Process (Maytansinoid Conjugate) Mab Two chemical reactions followed by purification to generate Ab-DMx conjugate Process can be designed to be highly robust and scalable Step 1 Linker Modification N--hydroxysuccinimide Modified Mab Step 2 DMx Conjugation Thiopyridine Mab-DMx

14 Analytical and Manufacturing Challenges in Developing Antibody-Drug Conjugates Analytical complexity and heterogeneity What assays are appropriate for quality assurance and characterization? What kind of analytical package is appropriate for justifying process changes? What are the analytical requirements for the conjugate versus its components? Talks by Marjorie Shapiro, Fred Jacobson and Nathan Ihle Demonstrating robustness of conjugate manufacturing processes Are the assays sufficiently discriminating? Is the complexity of the analytical challenge mirrored by process complexity? Can conjugation processes be designed to be robust?

15 Regulatory Considerations in Developing Antibody-Drug Conjugates Regulatory Jurisdiction A conjugate is composed of small molecule components (linker and cytotoxic agent) and an antibody What are the roles of divisions with expertise in the components (e.g. ONDQA and DMA)? With divided responsibility, how is review and interaction with the sponsor coordinated? Talks by Michael Folkendt and Tish Webber Classification of components (Antibody, Linker, Cytotoxic Agent) used to manufacture conjugates Is existing terminology appropriate (e.g. starting material, intermediate, API)? What are the consequences for testing, validation, process changes? Panel discussion

16 Analytical Complexity and Heterogeneity Additional assays required beyond those for an antibody due to presence of cytotoxic agent, e.g. Amount of free and bound cytotoxic agent Conjugation introduces heterogeneity on top of that already present in the antibody Antibody is heterogeneous due to, e.g. glycosylation, C-terminal Lysine Conjugation is to multiple sites on the antibody (generally not fully occupied)

17 Mass Spectrum of an Intact Conjugate Heterogeneity from Conjugation Adds to Heterogeneity from Antibody 00 The complexity of the spectrum is due to the presence of DMx molecules and N-linked glycans % mass D0 D1 D2 D3 D4 D5 D6 D7 Dn represents the number of DMx molecules per MAb

18 Deglycosylating the Conjugate Reveals Heterogeneity Due to Conjugation (Maytansinoid Distribution Profile) D3 100 D2 D4 D5 % D1 D6 D0 D Dn represents the number of DMx molecules per MAb mass

19 Mass Distribution Profile is a Good Test of Process Consistency UV based assay gives average maytansinoid loading MS provides orthogonal verification MS also provides information on relative amounts of antibodies loaded with 1, 2, 3, 4 etc. maytansinoids (without prior separation) MS also provides information on unconjugated antibody MS can detect other conjugation products, e.g. Crosslinked species Species with linker attached but no maytansinoid

20 Mass Distribution Profile of Three Conjugate Batches Sample Reference Standard Batch A Batch B 0D (naked Ab) 2.0 % 1.9% 1.6 % 1D 13.1 % 12.7% 11.2 % 2D 23.9 % 23.3 % 23.1 % MDP -- Relative abundance of maytansinoid species 3D 4D 24.1 % 19.3 % 24.2 % 19.5 % 24.5 % 20.2 % 5D 10.7 % 11.0 % 11.8 % 6D 5.2 % 5.7 % 6.1 % 7D 1.7 % 1.7% 1.9 % MAR By LC-MS By UV Mass distribution is very similar between batches Reasonable agreement between MAR (Maytansinoid/Antibody Ratio) by LC-MS and UV Other analytical methods also show consistency between these batches

21 Analytical Tools Can be Used to Show Comparability When Changes, e.g. Site, Scale, Are Made Antibody Manufacturer A Conjugation Site 1 Change in Conjugation Site and Scale Antibody Manufacturer A Conjugation Site 2 Change in Antibody Manufacturing Site Antibody Manufacturer B Conjugation Site 2

22 Mass Distribution Profile Shows Comparability After Process Changes 100 % % Ab Manufacturer B, Conjugation Site Ab Manufacturer A, Conjugation Site Ab Manufacturer A, Conjugation Site 2 % D 1 D 2 D 3 D 4 D 5 D 6 D 7 D Other analytical methods also show these batches are comparable mass

23 Robustness of Conjugate Manufacturing Processes Chemical reactions used to make conjugates have been studied for many years and are quite well understood Much of the separation required of the purification steps is of antibody/conjugate from solvents and low molecular weight species Process development and characterization shows that the chemistry and purification steps can be designed to be robust

24 How a Conjugation Process is Developed Single and Dual Point Experiments Identify key operating parameters Identify ranges for key operating parameters Test ranges (wider than operating range) Determine acceptable range DoE Studies Determine significant factors Identify interactions among key operating parameters Assess process variability Build predictive model and design robust process Determine operating ranges for manufacturing for a predictive outcome

25 Process Development and Characterization Starts with Single and Dual Factor Studies Modification Conc and Linker Titration Conjugate monomer vs modification conc and linker conc MAR M onom er (% ) Linker/Antibody Linker / Antibody Modification at 8 mg/ml Modification at 16 mg/ml Modification at 12 mg/ml Modification at 20 mg/ml Modification at 8 mg/ml Modification at 16 mg/ml Modification at 12 mg/ml Modification at 20 mg/ml MAR: Maytansinoid to Antibody Ratio

26 Results of a DoE Study: Predictive Model for MAR Response as Function of Two Process Parameters Design-Expert Software MAR X1 = C: Conj. Con. X2 = B: Linker Actual Factors A: Modi ph = 7.5 D: Conj. ph = 5.3 E: DM1 = 1.8 MAR B: Linker C: Conj. Con. Model can be built, allowing process parameters (and tolerances) to be selected to assure a consistent product MAR: Maytansinoid to Antibody Ratio

27 Conclusions Interest in Antibody Drug Conjugates is high and growing Conjugates are analytically challenging due to their complexity and heterogeneity There is regulatory complexity with conjugates due to split review responsibilities within the FDA Using the example of Mass Distribution Profile (by Mass Spectrometry): Heterogeneity due to the conjugate can be distinguished from that of the Antibody Results help to demonstrate batch consistency and comparability (in combination with other methods) Conjugation processes can be developed that are robust

28 Two Posters from ImmunoGen that may be of Interest Characterization of the Conjugation Sites in Cleavable Antibody-Maytansinoid Conjugates (Lazar et al) Degradation-Activity Relationship Assessment for IMGN242, an Antibody-Maytansinoid Conjugate (Lazar et al)

29 Acknowledgements Organizing Committee ImmunoGen Rajesh Krishnamurthy John Lambert Xinfang Li Alex Lazar Deb Meshulam