Phase I Infusion Trial

Condition: Chronic Lymphocytic Leukemia (CLL)
Product: ISF35 (Active Immune Therapy)
Location: M.D. Anderson Cancer Center (Houston, TX)
Principal Investigator: William G. Wierda, M.D., Ph.D.
Purpose: Evaluate toxicity, tolerability, and safety of ISF35

Status: Complete

Background

This Phase I infusion trial enrolled nine patients divided into three cohorts with increasing dose levels of ISF35. The median age was 70 years (range 30-77) and seven subjects were 70 years of age or older. Five were male (56%). The median number of prior treatments was two (range 0-3). Rai Stage was I/II (n=5) or IV (n=4). Four of the nine (44%) were 17p-deleted. Lymphocyte doubling times were six months or less in five of nine subjects (56%), and 12 months or less in eight of nine subjects (89%). Seven of nine subjects (78%) were ZAP-70-positive, three of nine (33%) were IgVH-unmutated, and eight of nine (89%) had β-2 microglobulin greater than 2.0 mg/L.

Safety Results

Safety results for all three dose-escalating cohorts demonstrated that autologous leukemia cells transduced to express the ISF35 molecule were well-tolerated and no dose-limiting toxicities were experienced at any of the dose levels evaluated. No maximum tolerated dose was identified. NCI-CTCAE Grade 2 anorexia, arthralgia, fatigue, fever, and malaise have been the most common side effects in subjects treated at the three dose levels. These side effects were transient (Fig 1, Fig 2) and resolved mostly within a one-week period. No dose response effects regarding toxicity have been observed, and no product-related Serious Adverse Events (SAE) have occurred in the treated patients. Significantly, unlike other standard therapies, ISF35 treatment was not immuno-suppressive and did not negatively impact T lymphocyte concentrations. In fact, T lymphocyte concentrations were increased for up to six weeks following ISF35 treatment.

Single Infusion of ISF35

After treatment with a single infusion of ISF35, an acute reduction of greater than 50% in absolute lymphocyte counts (ALC) was observed in six of nine patients. This reduction correlated with cell death as measured by the percentage of Annexin V positive cells. The decrease in ALC was prolonged in four of the patients with counts not returning to pretreatment levels for over three months. The prolonged response was not apparently dose-dependent as a long-term response was observed in patients from all three dosing cohorts.

In addition to the impact on patient ALC, ISF35 also had a major impact on lymph node sizes. All nine patients had acute reductions of at least 50% in lymph node sizes after treatment with ISF35. This response was more durable than the ALC reductions, as lymph node measurements were still more than 80% decreased in four patients 60 days after product administration.

17p- Patient Population

In the Phase I clinical trial, four patients out of nine had 17p- CLL. In three of these four patients, an acute reduction of greater than 50% in ALC was observed after the administration of the ISF35-treated autologous cells. Since these patients' cells lack functional p53, the induction of apoptosis in these cells must be due to the activation of non-p53 dependent pathways.

Significantly, in correlative samples taken from the ISF35-treated patients, the CLL cells isolated from all the 17p- patients became sensitive to chemotherapy in vitro at drug concentrations that are achievable using standard treatment regimens. The principal investigator, Dr. William Wierda, decided to treat two of the patients with standard fludarabine, cyclophosphamide, rituximab (FCR) regimens based on the in vitro findings and conceptual research published by himself and Dr. Thomas Kipps.

Both of these 17p- CLL patients achieved major responses (one clinical complete remission and one nodular partial remission) that were remarkable in a number of ways. First, the patients had 17p- CLL and would not be expected to achieve any response to standard chemotherapy. Second, the magnitude of the responses was unexpectedly large.

The first of the two 17p- patients (Fig 3), who had three prior Rituximab/high-dose steroid treatments and a lymphocyte doubling time of 5.2 months, received an initial course of FCR, the standard chemotherapy option for CLL, five months after ISF35 administration. Because this subject is 17p-, little to no response to FCR was expected. However, following the first course of fludarabine and cyclophosphamide (day 1) the patient's ALC plummeted from about 125 K/µL to 77.25 K/µL and was then reduced to 2.99 K/µL three weeks following the completion of the first round of FCR. The patient was subsequently given two additional courses of FCR and their ALC was last measured as 8.54 K/µL at 18 months post ISF35 treatment. A bone marrow biopsy detected a few remaining CLL cells in the patient's marrow resulting in the achievement of a nodular partial response. The patient was 78 years old at the time of this treatment and tolerated it well, achieving a durable remission lasting at least 12 months from when a clinical response was first observed.

The second 17p- patient (Fig 4), who had two prior Rituximab/high-dose steroid treatments and a lymphocyte doubling time of 6.5 months, received their first course of FCR nine and a half months after ISF35 administration. Their response was just as vigorous. The day after their first course of fludarabine and cyclophosphamide, the patient's ALC dropped from 141.07 K/µL to 48.2 K/µL and then declined to 8.15 K/µL two weeks following the completion of the first round of FCR. The patient was given three additional courses of FCR and was last evaluated as having an ALC of 0.56 K/µL at 13 months post ISF35 treatment. The patient tolerated the treatment well, while achieving a durable remission lasting at least three months from when a clinical response was first observed.

Based on these early results, it appears that CLL lymphocytes activated by a temporal exposure to ISF35 express elevated levels of pro-apoptotic proteins. The pro-apoptotic proteins include the p53 surrogate p73. CLL cells lacking the cellular machinery to undergo spontaneous cell death now once again became sensitive to standard chemotherapies. This sensitization of malignant B cells to standard chemotherapies by ISF35 may also be extended to other forms of leukemias, lymphomas, and solid tumor cancers. Ultimately, ISF35 may be used in combination with other chemo- and biologic therapies to greatly improve the therapeutic efficiencies of these agents while diminishing their toxicities.

Phase 1b Extension Results

As a follow-up to this Phase I clinical trial, four patients received at least one additional dose of ISF35. Each of the four patients that received repeat infusions experienced acute ALC decreases that were greater than those following the first product administration. One patient, with a lymphocyte doubling time of 6.8 months, received three ISF35 product administrations and, at last evaluation, had an ALC below the starting concentration 17 months after the first product administration. In addition to ALC reductions, further decreases in lymph node sizes were experienced by two of the patients. These reductions were equal to at least a 90% decline from their pre-treatment values and have lasted 14 months and 9 months as of their last reported exam.

These results demonstrate the prolonged durability of the response to ISF35 treatment following repeat administration. Additionally, this phase of the trial has demonstrated that repeat infusions of ISF35 can stabilize a patient's CLL, mitigate certain symptoms, and eliminate swelling in lymph nodes that can disfigure and damage internal organs. Therefore, patients who receive repeat infusions may be able to delay by years any chemotherapy and the immune and bone marrow suppression that accompanies it.

Conclusions

The treatment of CLL patients' disease with autologous ISF35-treated leukemic cells results in a reproducible reduction in circulating WBC concentrations and reduction in measured lymph node volumes. Repeat infusion of ISF35 augments the activity of this treatment and durable and long-lasting results can be achieved. Additionally, CLL B cell activation by ISF35 results in the up-regulation of a number of membrane-bound pro-apoptotic activator proteins such as CD95, DR5 and TNF receptor 1 and increased intracellular expression of a number of pro-apoptotic proteins including FADD, BID and p73. The activation of these factors increases the sensitivity of the patients' CLL cells to standard chemotherapy. For 17p- CLL patients, ISF35 treatment offers a potential therapeutic option for this form of the disease.