Clinical Responses to CAR.CD30-T Cells in Patients with CD30+ Lymphomas Relapsed after Multiple Treatments Including Brentuximab Vedotin

Background:

Infusion of chimeric antigen receptor modified T cells targeting the CD30 molecule and encoding the CD28 endodomain (CD30.CAR-Ts) in the absence of lymphodepleting chemotherapy has been shown to be safe with responses seen in patients (pts) with relapsed/refractory (r/r) CD30+ lymphomas (Ramos et al., JCI 2017). We present here the results of a phase 1b/2 trial of CD30.CAR-Ts administered after lymphodepleting chemotherapy in pts with r/r CD30+ Hodgkin (HL) and Non-Hodgkin lymphoma (NHL).

Methods:

The primary objective of the phase 1b portion of the study was to determine the recommended phase 2 dose level (RP2DL) of CD30.CAR-Ts using a standard 3+3 design. Two dose levels were tested: 1 x 10⁸ CAR-Ts/m² (DL1) and 2 x 10⁸ CAR-Ts/m² (DL2). For lymphodepletion, the first 8 pts (including the first 3 pts treated at DL1) received 2 days of bendamustine (benda) 90 mg/m², while the 10 remaining pts received 3 days of benda 70 mg/m² and fludarabine (flu) 30 mg/m², except for one pt who received only 1 day of benda and flu due to possible benda toxicity. Inclusion criteria were age ≥ 18 years, CD30+ disease, and r/r HL or NHL having failed ≥2 prior therapies.

Results:

At the time of data cut off (7/1/2018), 18 pts with a median age of 40.5 years (range: 23-70) had received CD30.CAR-Ts and undergone response assessment. Sixteen pts had HL, 1 had enteropathy associated T cell lymphoma, and 1 had Sezary syndrome. All pts were heavily pre-treated with a median of 8.5 prior therapies (range: 4-17). All pts had received prior brentuximab vedotin and 13 had prior checkpoint inhibitor therapy. Fourteen pts had prior autologous stem cell transplant (SCT) and 7 had prior allogeneic SCT.

Treatment was well tolerated with no dose limiting toxicities; as a consequence, the highest dose level of CAR-T cells (2 x 10⁸ CAR-Ts/m²) was given as the RP2DL. Three pts developed cytokine release syndrome (CRS) (grade 1: 2 pts and grade 2: 1 pt). Grade 1 CRS resolved spontaneously, while the pt with grade 2 CRS responded to tocilizumab. No neurotoxicity was observed.

Out of the 18 pts, 4 were in a complete response (CR) before infusion due to bridging chemotherapy and remained disease free at 6 wk follow up. Two of these pts have since relapsed with PFS of 3.8 months and 11.9 months while the other 2 pts are still in CR after 1 year of follow up. The 14 pts with evidence of disease pre-lymphodepletion were included in efficacy analysis. Of these 14 pts, 6 had a CR (43%, all in the benda/flu cohort), 1 had partial response (7%), 2 had stable disease (14%) and 5 had progressive disease (35%) at disease assessment. No responses occurred in the 3 pts treated at DL1. At median follow up of 138 days, the median PFS was 129 days. The median PFS for the 3 evaluable pts who received benda at DL1 was 55 days vs 172 days for the 9 pts who received benda/flu at DL2 (p = 0.039). The median PFS for the 2 evaluable pts at DL2 who received benda lymphodepletion was 85.5 days but this was not included in the comparison due to small sample size. Two out of 14 evaluable pts remain in CR at 1 year.

Using PCR on peripheral blood, CD30.CAR-Ts were found to be increased in the circulation of all pts, peaking at wk 2 post infusion, with increasing CAR-T cells in pts receiving greater number of CAR-T cells or more robust lymphodepletion (3.4x10³ ± 2.9x10³ copies/ug of DNA for DL1-beda vs. 61x10³ ± 41x10³ for DL2-benda vs. 59x10³ ± 22x10³ for benda/flu). These differences were confirmed by flow cytometry (CD3⁺CAR⁺ cells = 13%±9% for DL1-benda vs 21%±10% for DL2-benda vs 35%±8% for benda/flu). Persistence was also related to dose level and lymphodepletion (0.06x10³ ± 0.01x10³ vs 0.44x10³ ± 0.41x10³ vs 28x10³ ± 15x10³/ug of DNA at wk 4 for DL1-benda, DL2-benda, and benda/flu, respectively). Although both lymphodepletion regimens reduced the lymphocyte counts, only the combination of benda/flu was found to have a significant increase in IL-15 and IL-7 cytokines (13 fold, p<0.01 and 3 fold, p=0.016, respectively) that was sustained for 2 wks post infusion.

Conclusions:

We show that CD30.CAR-Ts combined with lymphodepletion with benda/ flu are safe and at 2 x 10⁸ CAR T cells/m² demonstrate excellent antitumor activity for pts with r/r CD30+ lymphomas. We also find that the addition of flu is critical for enhancing cytokines important for T cell growth and persistence. Finally, we demonstrate a significant PFS advantage in pts with r/r CD30+ lymphoma who received the highest dose level combined with benda and flu.